REVIEW. 87 



study of this question by the discussions which arose on the 

 results obtained by Davaine. 



2. The next section commences with the following statement : 

 Bacilli increase with enormous rapidity in the bloody and in the 

 fluids of the tissues of living animals, by increasing in length and 

 dividing transversely. As a convenient animal for injection 

 Koch uses mice, a small incision being made at the root of the 

 tail, and as small a drop as possible of the fluid containing the 

 Bacilli being injected into the system ; to see whether these 

 organisms did not after a time pass into another form, and that 

 he might also be provided with fresh material, Cohn injected 

 several mice — once as many as twenty — one after the other, each 

 succeeding mouse from the one that had preceded it. The 

 results were always the same; the spleen was enormously swollen, 

 and filled with a large number of crystalline-looking rods of 

 varying size, never exhibiting movement or spore formation ; 

 they increased in number solely by division. 



The number of Bacilli found in the blood varies with the ani- 

 mal injected ; in the guinea-pig it was enormous, sometimes 

 even exceeding that of the blood-corpuscles ; in the rabbit much 

 smaller, so that sometimes several drops had to be examined 

 before any were found ; in the mouse often nil. 



The next statement is : in the blood of dead animals, or in 

 other suitable fluids, the Bacilli grow to very long, straight, 

 leptothrix-like filaments (within certain limits of temperature and 

 with the presence of air), while the formation of numerous spores 

 goes on at the same time. 



The truth of this statement can be tested very easily by drop- 

 ping a minute portion of a spleen thus affected into some per- 

 fectly fresh serum, or Humor aqiieus of a cow. The means which 

 Koch employed for preventing evaporation will be found in his 

 paper. After the specimen has been kept for fifteen or twenty 

 hours at a temperature of 35° to 37° it may be examined ; the 

 centre will be found almost unchanged, of the appearance repre- 

 sented in the accompanying woodcut. As the centre is left, 

 elongated and bent forms are met with, till, towards the edge of 

 the glass cover, fibres are found more than a hundred times 

 the length of the rods in the middle of the glass. Of these 

 last many will be found to have lost their crystalhne appearance 

 and homogeneous structure, their contents being finely granu- 

 lated, and small highly-refractive granules being set at regular 

 distances from one another. Quite at the edge, the fibres con- 

 tain perfectly formed spores of an oval shape and highly refrac- 

 tive, resembling a string of pearls. 



After much exercise of patience and ingenuity the author was 

 at last able to watch the steps of spore formation under the 



