ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
387 
larger black circular image, surrounded by a smaller and smaller white 
circle, until at length an image was obtained in the thickness of the 
valve where the pearls take their origin. The image was then hexagonal. 
Deformed Diatoms.* — Dr. J. D. Cox describes a number of specimens 
of diatoms which are deformed in the following ways, viz. : — (1) in- 
dented or deformed outlines ; (2) double or multiple centre in the 
scheme of marking; (3) marking unsymmetrically varied. He thinks 
that a further study of this subject may have the effect of reducing the 
enormous catalogue of species of diatoms. 
j8. Schizomycetes. 
Bacteria and Disease4 — In a lecture on the connection between 
bacteria and the poisons of disease, Prof. Brieger, after alluding to the 
early historical aspects of the subject, takes as his keynote the aphorism 
invented by Mitscherlich, that Life is but Putrefaction. He then passes 
on to consider the alkaloidal bases met with in the human body. The 
aromatic series, such as indol, skatol, carbolic acid, kresol, are passed 
over rapidly, as being of little import. He then divides the products of 
bacterial metabolism into toxines and ptomaines, according as they are 
poisonous or non-poisonous. He then proceeds to show how closely 
connected these bodies are with the presence of bacteria and the process 
of digestion ; for example, when fibrin is digested with pepsin, a poison, 
peptotoxin, is produced which kills the lower animals with palsy of the 
posterior extremities. So too from decomposing flesh can be isolated 
neuridin, cadaverin, putrescin, and certain toxines, as neurin, methyl- 
guanidin, mydatoxin, and a fourth isomerous with typhotoxin. Another 
toxine, alluded to at some length on account of its fatality and special 
character, is mytilotoxin, a poison found in mussels. 
The author next proceeds to notice these ptomaines and toxines 
which are the direct derivatives of pathogenic bacteria. The first 
alluded to are Staphylococcus pyogenes aureus and Streptococcus pyogenes. 
These micro-organisms, which are intimately connected with pyaemia 
and septicaemia, show, however, important chemical differences ; for the 
former when cultivated in meat broth throws off ammonia, and the latter 
trimethylamin. 
The bacillus of typhoid is responsible for typhotoxin, and the cholera 
bacillus for several, such as penta- and tetramethylendiamin, methyl- 
guanidin, and certain specific toxines. Passing over the toxines of 
tetanus and anthrax, we may notice that four authors are quoted who 
have found that that curious disease cystinuria is due to an intestinal 
mycosis, and must therefore be placed among infectious diseases. 
The specific action of the various toxines is regarded as a conclusive 
proof of the constancy of the species of bacteria. 
Infection of Vicia Faba by Bacillus radicicola.if — By an apparatus 
contrived for the purpose, Herr M. W. Beyerinck has been able to infect 
plants of Vicia Faba by Bacillus radicicola , and thus to induce the forma- 
tion of the well-known tubercles on the root. He finds these bacilli to 
* Proc. Araer. Soc. Micr., 1890, pp. 178-83 (1 pi.). 
t Biol. Centralbl., x. (1890) pp. 364-73. 
% Bot. Ztg., xlviii. (1890) pp. 837-43 (1 fig.). 
