ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
791 
protective power, and consequently these experiments indicated a 
difference in the mode of action of defensive proteids of immune and 
non-immune animals respectively. Further, the amount of defensive 
proteid present in a rat could be diminished by the causes which were 
known to he capable of lowering the animal’s power of resisting anthrax. 
For instance, Feser stated that rats become susceptible to anthrax when 
fed on a vegetarian diet. Mr. Hankin obtained similar results with wild 
rats. The ordinary white rat he found to be generally refractory to 
anthrax on any diet, and the defensive proteid could always be obtained 
from its spleen and blood-serum. This was not the case with wild rats. 
In one experiment eight wild rats were used ; of these, four were fed on 
bread and meat, the others on plain bread, for about six weeks. Then 
one rat of each lot was inoculated with anthrax ; of these, the one that 
had been subjected to a bread diet succumbed. The remaining rats were 
killed, and it was found that while the spleens of the flesh-fed rats 
contained abundance of the defensive proteid, only traces of this substance 
could be obtained from the spleens of the rats that had been fed on 
bread alone. A similar result was obtained in other experiments. 
Very young rats were known to be susceptible to anthrax, and so far 
as could be judged from the litmus test (after dialysis and addition of 
NaCl), their serum appeared to contain less of the defensive proteid than 
did that of the adult rat. Further, Mr. Hankin found that a young rat 
could be preserved from anthrax by an injection of its parent’s blood- 
serum. 
These facts appeared to prove that the defensive proteid of the rat 
deserved its name, in that it preserves the animal from the attack of the 
anthrax microbe ; in other words, that this substance was at any rate a 
part cause of a rat’s immunity against anthrax. 
Defensive proteids appeared to be ferment-like, albuminous bodies, 
and it was extremely unlikely that we should for a considerable time be 
able to classify them by any other than physiological tests. From this 
point of view it was possible to divide them into two classes ; first, those 
occurring naturally in normal animals, and secondly, those occurring in 
animals that have artificially been made immune. For these two classes 
Mr. Hankin proposed the names of sozins and phylaxins. A “ sozin ” 
was a defensive proteid that occurred naturally in a normal animal. 
They had been found in all animals yet examined, and appear to act on 
numerous kinds of microbes, or on their products. A “ phylaxin ” was 
a defensive proteid which was only found in an animal that had been 
artificially made immune against a disease, and which (so far as is yet 
known) only acted on one kind of microbe or on its products. 
Each of these classes of defensive proteids could obviously be further 
subdivided into those that acted on the microbe itself, and those that 
acted on the poisons it generated. These sub-classes he proposed to 
denote by adding the prefixes myco- and toxo- to the class name. Thus 
myco-sozins were defensive proteids occurring in the normal animal, 
which had the power of acting on various species of microbe. Toxo-sozins 
were defensive proteids, also occurring in the normal animal, having the 
power of destroying poisons produced by various microbes. Myco- 
phylaxins and toxo-phylaxins similarly would denote the two sub-classes 
of the phylaxin group. 
