April i6, 1896] 



NATURE 



569 



relation existing between the pupillary contraction and the 

 illumination of the retina. 



The discovery of the direct action of light upon the iris leads 

 to a number of curious deductions. 



1. We are now able to explain the cause of the intense photo- 

 phobia which characterises the iritis, and it is probable that the 

 examination of the iris by the new jjupilometer fr(5m the point 

 of view of its proper excitability will be very useful in the 

 diagnosis of diseases of the eye. 



2. It shows that our photometric measurements must involve 

 a systematic error, although slight. When the eye is directed 

 towards the most luminous of two lights of different intensities 

 the iris contracts, tending thus to equalise for the retina the two 

 lights. It is in this movement of the iris perhaps that we should 

 seek an explanation of the contradictions which we meet 

 continually between the data of our photometric processes and 

 the data furnished by sensitive plants employed in the measure- 

 ment of light. We know, for instance, that a branch of vitia 

 sativa placed between two lights equal for our eye and equi- 

 distant from each other tends invariably to incline towards one 

 of them. Charles Henry. 



IMMUNISATION AGAINST SERPENTS 

 'ENOM,AND THE TREATMENT OF SNAKE- 

 BITE WITH ANTIVENENE.^ 



"Lj'ROM a remote period of antiquity, there has been enmity 

 -^ between the human race and serpents, and, in a literal 

 sense, man has bruised the head of the serpent, and the serpent 

 has bruised the heel of man. This long-continued feud has not 

 yet resulted in victory for either side. Venomous serpents still 

 annually destroy the lives of tens of thousands of human beings, 

 and, in self-defence, tens of thousands of serpents are annually 

 slain by man. 



The progress of knowledge has greatly increased the means 

 for protecting mankind against the death-producing effects of 

 many diseases ; and, although these means have been liberally 

 employed in the contest against venomous serpents, none of 

 them has hitherto been found sufficient. 



The reality of the contest is appreciated when we find per- 

 vading medical literature from its earliest beginnings — from the 

 time of Pliny and Celsus — to the present time, disquisitions on 

 the treatment of the bites of venomous serpents, and lengthy 

 descriptions of the numerous remedies, organic and inorganic, 

 that have been used for this purpose. Although extended 

 experience and the application of the scientific methods of 

 the present day, have resulted in showing that each of these 

 remedies had been recommended on insufficient grounds, we 

 may hesitate in pronouncing their recommendation to have 

 been premature, in view of the impossibility of waiting, in the 

 presence of imminent dangers, until accurate demonstration has 

 been obtained by the usually tardy and laborious processes of 

 science. 



Let me pause here for a few minutes t<^ indicate the practical 

 importance of a scientific demonstration of the value of any 



inedy that is used in the treatment of snake-poisoning. 



When a serpent inflicts a wound, I need scarcely say that it is 



; the wound, but the venom introduced into it which causes 

 symptoms of poisoning, and the death that may result. This 



nom is now known to be a complex mixture, containing several 



ii-poisonous as well as poisonous substances. The latter are 

 not ferments and have no power of reproducing themselves in 

 the body, but they are substances that produce effects having a 

 direct relationship to the quantity introduced into the body. 

 This quantity in the case of each serpent varies with its size and 

 bodily and mental condition ; with the nature of the bite— 

 whether both fangs or only one have been introduced, whether 

 they have penetrated deeply or only scratched the surface ; and 

 with other circumstances related to the serpent, such as whether 

 it had recently bitten an animal or not, and thus parted with a 

 portion or retained the whole of the venom stored in the poison 

 glands. 



A bite may, therefore, result in very little danger, or it may 

 rapidly fatal ; but, in order to produce death, there must 



ve been introduced into the tissues at least a certain quantity 



' An address delivered at the Royal Institution of Gre.nt Britain, on 

 •■ u'.ay, March 20, by Prof. Thomas R. Fraser, F. R.S. 



NO. I 38 I, VOL. 53] 



of venom, which i." spoken of as the minimum-lethal quantity 

 or dose. The minimum-lethal quantity for the animal bitten, 

 again, is different for different species of animals, and different 

 also for different individuals of the same species, the chief cause 

 of difference between animals of the same species being the 

 body weight of the individual, the quantity required to produce 

 death being very exactly related to each pound or kilogramme of 

 weight. 



If even a minute fraction below the minimum-lethal has beer^ 

 introduced into the tissues by an effective bite, death will not 

 follow, although serious and alarming symptoms will be pro- 

 duced of exactly the same kind as those which follow a bite 

 which terminates fatally. 



How then can we be assured, in any case of snake-bite in man, 

 that a quantity of venom sufficient to produce death has been in- 

 troduced ? It is impossible to answer this question except by 

 the result. If a quantity less than the minimum-lethal has been 

 introduced, although the gravest symptoms may be produced, 

 the patient will recover whatever remedies are administered, 

 provided, obviously, that the remedies have not been so in- 

 judiciously selected or used that they themselves, and not the 

 insufficient quantity of venom, produce a fatal termination. 

 The recovery of a patient after the introduction of less than the 

 smallest quantity of venom capable of producing death, has thus 

 too often been attributed to the remedies that have been ad- 

 ministered ; and consequently, as, indeed, is exemplified in the 

 treatment of many diseases, a large number of substances have 

 acquired an unjust reputation as antidotes. The list of anti- 

 dotes has, accordingly, become a very large one ; but when 

 their pretensions have been subjected to sufficient tests, the 

 verdict is that all of them are valueless to prevent death when 

 even the smallest quantity of venom required to produce death 

 has been received by an animal. 



Without entering into details, I will content myself with re- 

 producing the opinion of Sir Joseph Fayrer, that, " after long 

 and repeated observations in India, and subsequently in England, 

 I am forced to the conclusion that all the remedies hitherto 

 regarded as antidotes are absolutely without any specific effect 

 on the condition produced by the poison." 



But while medical practice and science, in each period of its 

 development, has thus failed to protect man against this ancient 

 enemy, legendary traditions, the tales of travellers and of resi- 

 dents among nations and tribes existing outside of the civilisa- 

 tion of the time, at least suggest that, by means apart from the 

 use of remedies, some measure of success may actually have 

 been obtained. 



Many of these legends and statements are probably of great 

 significance, and, in connection with facts derived from ex- 

 periment, which to-night I have to describe, they possess a deep 

 interest. 



We learn from these legends that from a remote period of 

 time the belief has existed that a power may be acquired by 

 man of freely handling venomous serpents, and even of success- 

 fully resisting the poisonous effects of their bites. 



The Psylli of Africa, the Marsi of Italy, the Gouni of India, 

 and other ancient tribes and sects, were stated to have been 

 immune against serpents' bites, and this immunity has been 

 explained on the supposition that serpents' blood was present in 

 the veins of the members of these tribes and sects. 



In more modern times and, indeed, at the present day, the 

 same belief is expressed in the writings of many travellers. In 

 "A New and Accurate Description of the Coast of Guinea," by 

 William Bosnian, published in 1705, an account is given of the 

 great "reverence and respect" of the negroes for snakes, 

 worshipped by them as gods ; in connection with which the 

 following statements are made. "But what is best of all is 

 that these idolatrous snakes don't do the least mischief in the 

 world to mankind ; for if by chance in the dark one treads upon 

 them, and they bite or sting him, it is not more prejudicial than 

 the sting of millipedes. Wherefore the natives would fain 

 persuade us that it is good to be bitten or stung by these snakes, 

 upon the plea that one is thereby secured and protected from 

 the sting of any poisonous snake" (p. 379). 



At Southern Africa, the Rev. John Campbell, in 1813, 

 observed that it was " very common among the Hottentots to 

 catch a serpent, squeeze out the poison from under his teeth, 

 and drink it. They say it only makes them a little giddy, and 

 imagine that it preserves them afterwards from receiving any 

 injury from the sting of that reptile" (p. 401). 



Drummond Hay, in his work on Western Barbary, pub- 



