Before I followed them I witnessed an incident worthy of note from the standpoint of a naturalist, and of possible importance to us because of the trip we were about to take. South America, even more than Australia and Africa, and almost as much as India, is a country of poisonous snakes. As in India, although not to the same degree, these snakes are responsible for a very serious mortality among human beings. One of the most interesting evidences of the modern advance in Brazil is the establishment near Sao Paulo of an institution especially for the study of these poisonous snakes, so as to secure antidotes to the poison and to develop enemies to the snakes themselves. We wished to take into the interior with us some bottles of the anti-venom serum, for on such an expedition there is always a certain danger from snakes. On one of his trips Cherrie had lost a native follower by snake-bite. The man was bitten while out alone in the forest, and, although he reached camp, the poison was already working in him, so that he could give no intelligible account of what had occurred, and he died in a short time.

Poisonous snakes are of several different families, but the most poisonous ones, those which are dangerous to man, belong to the two great families of the colubrine snakes and the vipers. Most of the colubrine snakes are entirely harmless, and are the common snakes that we meet everywhere. But some of them, the cobras for instance, develop into what are on the whole perhaps the most formidable of all snakes. The only poisonous colubrine snakes in the New World are the ring- snakes, the coral-snakes of the genus elaps, which are found from the extreme southern United States southward to the Argentine. These coral-snakes are not vicious and have small teeth which cannot penetrate even ordinary clothing. They are only dangerous if actually trodden on by some one with bare feet or if seized in the hand. There are harmless snakes very like them in color which are sometimes kept as pets; but it behooves every man who keeps such a pet or who handles such a snake to be very sure as to the genus to which it belongs.

The great bulk of the poisonous snakes of America, including all the really dangerous ones, belong to a division of the widely spread family of vipers which is known as the pit-vipers. In South America these include two distinct subfamilies or genera—whether they are called families, subfamilies, or genera would depend, I suppose, largely upon the varying personal views of the individual describer on the subject of herpetological nomenclature. One genus includes the rattlesnakes, of which the big Brazilian species is as dangerous as those of the southern United States. But the large majority of the species and individuals of dangerous snakes in tropical America are included in the genus lachecis. These are active, vicious, aggressive snakes without rattles. They are exceedingly poisonous. Some of them grow to a very large size, being indeed among the largest poisonous snakes in the world—their only rivals in this respect being the diamond rattlesnake of Florida, one of the African mambas, and the Indian hamadryad, or snake-eating cobra. The fer-de-lance, so dreaded in Martinique, and the equally dangerous bushmaster of Guiana are included in this genus. A dozen species are known in Brazil, the biggest one being identical with the Guiana bushmaster, and the most common one, the jararaca, being identical, or practically identical with the fer-de-lance. The snakes of this genus, like the rattlesnakes and the Old World vipers and puff-adders, possess long poison-fangs which strike through clothes or any other human garment except stout leather. Moreover, they are very aggressive, more so than any other snakes in the world, except possibly some of the cobras. As, in addition, they are numerous, they are a source of really frightful danger to scantily clad men who work in the fields and forests, or who for any reason are abroad at night.

The poison of venomous serpents is not in the least uniform in its quality. On the contrary, the natural forces—to use a term which is vague, but which is as exact as our present-day knowledge permits— that have developed in so many different families of snakes these poisoned fangs have worked in two or three totally different fashions. Unlike the vipers, the colubrine poisonous snakes have small fangs, and their poison, though on the whole even more deadly, has entirely different effects, and owes its deadliness to entirely different qualities. Even within the same family there are wide differences. In the jararaca an extraordinary quantity of yellow venom is spurted from the long poison-fangs. This poison is secreted in large glands which, among vipers, give the head its peculiar ace-of-spades shape. The rattlesnake yields a much smaller quantity of white venom, but, quantity for quantity, this white venom is more deadly. It is the great quantity of venom injected by the long fangs of the jararaca, the bushmaster, and their fellows that renders their bite so generally fatal. Moreover, even between these two allied genera of pit-vipers, the differences in the action of the poison are sufficiently marked to be easily recognizable, and to render the most effective anti-venomous serum for each slightly different from the other. However, they are near enough alike to make this difference, in practice, of comparatively small consequence. In practice the same serum can be used to neutralize the effect of either, and, as will be seen later on, the snake that is immune to one kind of venom is also immune to the other.

But the effect of the venom of the poisonous colubrine snakes is totally different from, although to the full as deadly as, the effect of the poison of the rattlesnake or jararaca. The serum that is an antidote as regards the colubrines. The animal that is immune to the bite of one may not be immune to the bite of the other. The bite of a cobra or other colubrine poisonous snake is more painful in its immediate effects than is the bite of one of the big vipers. The victim suffers more. There is a greater effect on the nerve-centres, but less swelling of the wound itself, and, whereas the blood of the rattlesnake's victim coagulates, the blood of the victim of an elapine snake—that is, of one of the only poisonous American colubrines— becomes watery and incapable of coagulation.

Snakes are highly specialized in every way, including their prey. Some live exclusively on warm-blooded animals, on mammals, or birds. Some live exclusively on batrachians, others only on lizards, a few only on insects. A very few species live exclusively on other snakes. These include one very formidable venomous snake, the Indian hamadryad, or giant cobra, and several non-poisonous snakes. In Africa I killed a small cobra which contained within it a snake but a few inches shorter than itself; but, as far as I could find out, snakes were not the habitual diet of the African cobras.

The poisonous snakes use their venom to kill their victims, and also to kill any possible foe which they think menaces them. Some of them are good-tempered, and only fight if injured or seriously alarmed. Others are excessively irritable, and on rare occasions will even attack of their own accord when entirely unprovoked and unthreatened.

On reaching Sao Paulo on our southward journey from Rio to Montevideo, we drove out to the "Instituto Serumtherapico," designed for the study of the effects of the venom of poisonous Brazilian snakes. Its director is Doctor Vital Brazil, who has performed a most extraordinary work and whose experiments and investigations are not only of the utmost value to Brazil but will ultimately be recognized as of the utmost value for humanity at large. I know of no institution of similar kind anywhere. It has a fine modern building, with all the best appliances, in which experiments are carried on with all kinds of serpents, living and dead, with the object of discovering all the properties of their several kinds of venom, and of developing various anti-venom serums which nullify the effects of the different venoms. Every effort is made to teach the people at large by practical demonstration in the open field the lessons thus learned in the laboratory. One notable result has been the diminution in the mortality from snake-bites in the province of Sao Paulo.

In connection with his institute, and right by the laboratory, the doctor has a large serpentarium, in which quantities of the common poisonous and non-poisonous snakes are kept, and some of the rarer ones. He has devoted considerable time to the effort to find out if there are any natural enemies of the poisonous snakes of his country, and he has discovered that the most formidable enemy of the many dangerous Brazilian snakes is a non-poisonous, entirely harmless, rather uncommon Brazilian snake, the mussurama. Of all the interesting things the doctor showed us, by far the most interesting was the opportunity of witnessing for ourselves the action of the mussurama toward a dangerous snake.

The doctor first showed us specimens of the various important snakes, poisonous and non-poisonous, in alcohol. Then he showed us preparations of the different kinds of venom and of the different anti-venom serums, presenting us with some of the latter for our use on the journey. He has been able to produce two distinct kinds of anti-venom serum, one to neutralize the virulent poison of the rattlesnake's bite, the other to neutralize the poison of the different snakes of the lachecis genus. These poisons are somewhat different and moreover there appear to be some differences between the poisons of the different species of lachecis; in some cases the poison is nearly colorless, and in others, as in that of the jararaca, whose poison I saw, it is yellow.

But the vital difference is that between all these poisons of the pit- vipers and the poisons of the colubrine snakes, such as the cobra and the coral-snake. As yet the doctor has not been able to develop an anti-venom serum which will neutralize the poison of these colubrine snakes. Practically this is a matter of little consequence in Brazil, for the Brazilian coral-snakes are dangerous only when mishandled by some one whose bare skin is exposed to the bite. The numerous accidents and fatalities continually occurring in Brazil are almost always to be laid to the account of the several species of lachecis and the single species of rattlesnake.

Finally, the doctor took us into his lecture-room to show us how he conducted his experiments. The various snakes were in boxes, on one side of the room, under the care of a skilful and impassive assistant, who handled them with the cool and fearless caution of the doctor himself. The poisonous ones were taken out by means of a long-handled steel hook. All that is necessary to do is to insert this under the snake and lift him off the ground. He is not only unable to escape, but he is unable to strike, for he cannot strike unless coiled so as to give himself support and leverage. The table on which the snakes are laid is fairly large and smooth, differing in no way from an ordinary table.

There were a number of us in the room, including two or three photographers. The doctor first put on the table a non-poisonous but very vicious and truculent colubrine snake. It struck right and left at us. Then the doctor picked it up, opened its mouth, and showed that it had no fangs, and handed it to me. I also opened its mouth and examined its teeth, and then put it down, whereupon, its temper having been much ruffled, it struck violently at me two or three times. In its action and temper this snake was quite as vicious as the most irritable poisonous snakes. Yet it is entirely harmless. One of the innumerable mysteries of nature which are at present absolutely insoluble is why some snakes should be so vicious and others absolutely placid and good-tempered.

After removing the vicious harmless snake, the doctor warned us to get away from the table, and his attendant put on it, in succession, a very big lachecis—of the kind called bushmaster—and a big rattlesnake. Each coiled menacingly, a formidable brute ready to attack anything that approached. Then the attendant adroitly dropped his iron crook on the neck of each in succession, seized it right behind the head, and held it toward the doctor. The snake's mouth was in each case wide open, and the great fangs erect and very evident. It would not have been possible to have held an African ring-necked cobra in such fashion, because the ring-neck would have ejected its venom through the fangs into the eyes of the onlookers. There was no danger in this case, and the doctor inserted a shallow glass saucer into the mouth of the snake behind the fangs, permitted it to eject its poison, and then himself squeezed out the remaining poison from the poison- bags through the fangs. From the big lachecis came a large quantity of yellow venom, a liquid which speedily crystallized into a number of minute crystals. The rattlesnake yielded a much less quantity of white venom, which the doctor assured us was far more active than the yellow lachecis venom. Then each snake was returned to its box unharmed.

After this the doctor took out of a box and presented to me a fine, handsome, nearly black snake, an individual of the species called the mussurama. This is in my eyes perhaps the most interesting serpent in the world. It is a big snake, four or five feet long, sometimes even longer, nearly black, lighter below, with a friendly, placid temper. It lives exclusively on other snakes, and is completely immune to the poison of the lachecis and rattlesnake groups, which contain all the really dangerous snakes of America. Doctor Brazil told me that he had conducted many experiments with this interesting snake. It is not very common, and prefers wet places in which to live. It lays eggs, and the female remains coiled above the eggs, the object being apparently not to warm them, but to prevent too great evaporation. It will not eat when moulting, nor in cold weather. Otherwise it will eat a small snake every five or six days, or a big one every fortnight.

There is the widest difference, both among poisonous and non-poisonous snakes, not alone in nervousness and irascibility but also in ability to accustom themselves to out-of-the-way surroundings. Many species of non-poisonous snakes which are entirely harmless, to man or to any other animal except their small prey, are nevertheless very vicious and truculent, striking right and left and biting freely on the smallest provocation—this is the case with the species of which the doctor had previously placed a specimen on the table. Moreover, many snakes, some entirely harmless and some vicious ones, are so nervous and uneasy that it is with the greatest difficulty they can be induced to eat in captivity, and the slightest disturbance or interference will prevent their eating. There are other snakes, however, of which the mussurama is perhaps the best example, which are very good captives, and at the same time very fearless, showing a complete indifference not only to being observed but to being handled when they are feeding.