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Pn ee Se 
JANvary 20, 1923 
NATURE 
87 

leucocytes triturated at a temperature of liquid air, 
failed to demonstrate bactericidal bodies for B. typhosus 
in rabbit leucocytes. The leucocytic extracts of the hen 
have, according to Schneider, no action on B. typhosus, 
but a very considerable action on B. anthracis. On the 
other hand, the serum of the hen can kill B. typhosus, 
but has little action on B. anthracis, so that it would 
seem that absence of bactericidal property in the 
- extract of a cell might be compensated by its presence 
in the surrounding fluid, and vice versa. The study 
of bactericidal bodies in tissue extracts and body 
secretions is again being actively pursued in connexion 
with bacteriophage problems. In the so-called bacterio- 
phage, from whatever source it may be obtained, there 
is exhibited the same thermostability and the same 
limitation of action to certain bacterial groups. Rapidity 
of action of these leucocytic extracts on organisms of 
the subtilis group and slowness of action on organisms 
like B. typhosus, with subsequent over-growth of pre- 
sumably resistant organisms, are features which recall 
those noted in investigations connected with the 
bacteriophage and with the bactericidal bodies present 
in egg-white as demonstrated by Rettger and Fleming. 
I may close this subject by noting the existence of 
the thermostable bactericidal body in rat serum. This 
body has been carefully tested by Pirenne against 
organisms of the subtilis group, and also organisms 
like B. coli and B. pyocyaneus. Plating experiments 
have shown that organisms like B. mycoides, B. 
megatherium, B. subtilis are rapidly killed off, while 
B. proteus, B. coli, and B. pyocyaneus multiply freely. 
The cholera vibrio is also killed off, but this action was 
found to be due to the ordinary thermolabile alexin in 
the rat serum and it disappeared after inactivation of 
the serum. 
There remain only the proteolytic bodies contained 
in leucocytes, which have been studied by many 
workers chiefly in connexion with the so-called anti- 
tryptic action of serum. We know little or nothing 
of their action on bacteria, and indeed it would be 
difficult to separate any such action exhibited from 
that due to the more generally studied endolysins. I 
may just mention the alleged existence of bactericidal 
bodies in platelets, a subject introduced by Gruber 
and Futaki in 1907, and but little studied since. These 
authors came to the conclusion that the bactericidal 
action on anthrax of normal rabbit serum (a highly 
susceptible animal) depended on substances derived 
from the platelets. Barreau, who continued this work, 
found that the serum of the dog (a highly resistant 
animal to anthrax) had no action on anthrax nor had 
its platelets. He concluded, however, that the platelet 
bactericidal bodies or plakins probably did not play 
much part in natural resistance, as the rat, for 
example, a resistant animal, was rich in plakins, while 
the rabbit, a susceptible animal, was equally so. It is 
possible that the recent work on the purely mechanical 
function of blood platelets in removing suspended 
organisms by virtue of their adhesive properties may 
throw a different light on these alleged bactericidal 
substances in platelets. 
ANIMAL EXPERIMENTS. 
The application of these defence mechanisms to the 
elucidation of natural resistance to anthrax can now 
NO. 2777, VOL. L11] 
be very shortly considered. The resistant animals 
chiefly studied have been the frog, the fowl (especially 
the hen and pigeon), the rat, and the dog, but we 
have no accurate data of a quantitative kind as to 
the extent of this resistance in most cases. There is 
no doubt that the frog presents an extraordinary 
resistance to anthrax infection—a resistance which 
in the early days was attributed to its low body tem- 
perature. Attempts were made to infect frogs kept at 
37° C., and in these circumstances the animals readily 
succumbed. Metchnikoff attributed the deaths in 
these cases to diminished phagocytic action, whereas 
in the frog whose temperature was not interfered with, 
exuberant phagocytosis at the seat of inoculation 
afforded sufficient explanation of the immunity. The 
humoralists, however, maintained that the immunity 
was due to the bactericidal properties of the local lymph 
(Nuttall, Baumgarten, Petruschky, etc.). Metchnikoff 
countered this by showing that B. anthracis could 
grow readily in frog plasma. Galli-Valerio favoured 
the combined action of phagocytosis and bactericidal 
property of lymph as the most likely explanation. 
The matter remains quite obscure, and a more recent 
worker, Ditthorn, simply states that anthrax rods 
inoculated in any way into frogs show degenerative 
changes in a few days and lose their contours. The 
test organisms may, of course, play a decisive réle 
in view of the fact that Dieudonné, for example, 
cultivated a race of anthrax growing abundantly at 
12° C., and with it succeeded in killing frogs readily. 
These experiments require confirmation. 
With regard to fowls, the hen and pigeon, and 
particularly the former, are known to possess high 
resistance, and in the classical experiments of Pasteur 
and Joubert, in 1878, the immunity was attributed to 
the high body temperature of the fowl. By immersing 
the fowl in cold water infection took place. The death 
in such circumstances has been attributed by later 
workers to a general lowering of resistance, and not 
to an inability on the part of B. anthracis to grow 
at the high temperature of the fowl. Metchnikoff 
maintained that phagocytosis in the normal hen was 
rapid and complete, and in the cooled hen very poor. 
Later, Thiltges stated that phagocytosis was not in 
evidence, and that the immunity was due to the 
bactericidal action of the plasma, a property which 
Gengou denied. Thiltges agreed, however, with 
Metchnikoff in the matter of the pigeon. Bail and 
Petterson and Schneider ascribe the resistance to the 
action of the hen leukins, which act very powerfully on 
B. anthracis, while the serum has relatively little action. 
Donati in a more recent communication ascribes the 
immunity of the fowl simply to a local invasion of 
leucocytes, which hinder capsule formation, and by 
virtue of bactericidal substances secreted by them, and 
not by phagocytosis, secure the removal of the invaders. 
It is notorious that the adult dog can tolerate without 
inconvenience the inoculation of large quantities of 
bacilli, and, as one might expect, this immunity has 
been attributed by Metchnikoff to phagocytosis at the 
site of inoculation. Hektoen later showed that in the 
presence of dog serum dog leucocytes readily took up 
B. anthracis. \t would appear that the serum of the 
dog has but little or no anthracidal action as compared, 
for example, with that of the rabbit, which is, on the 
