ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 431 



He is inclined, therefore, to tliink that the microbe of rabies is 

 infinitely small, a mere dot in shape, and not like a bacillus or a 

 dumbbell-shaped micrococcus. 



The only method known at present by which these granulations 

 may be isolated from the other and nervous elements is the following : 

 — Virus taken from the brain of an animal that has died of rabies is 

 injected into the veins of a rabid animal at the moment when asphyxia 

 commences. In a short time the normal nervous elements disappear 

 from the blood in which only the just-mentioned minute granulations 

 are now to be found. These may be stained by anilin dyes, but as the 

 author is careful to point out, it is not yet definitely proved that these 

 granulations are the microbes of rabies. 



It has been found that while the trepanation- experiments are 

 succeeded by desire to bite and " rabid barking " — furious rabies — 

 injection experiments produce only paralytic rabies. If, however, 

 exceedingly minute quantities of virus are injected, furious rabies 

 ensues. On the other hand these minute quantities extend the period 

 of incubation, and if the poison is diluted beyond a certain extent the 

 inoculation has no effect. But these minute and inoffensive doses do 

 not give protection against the effect of larger doses. 



In rare cases the effects of the poison disappear to reappear with 

 mortal result after some days. Entirely negative results have been 

 obtained in reference to the pretended diminution of the poison 

 by the influence of cold and by its passage from the mother to the 

 foetus. 



Especial attention has been given to the very important question 

 of the alteration of the character of the virus, and it has been found 

 that the passage of the rabic virus through several species does more 

 or less profoundly modify its virulence. Pasteur and his assistants 

 now possess a virus which gives rabies to the rabbit in seven or eight 

 days, and that with remarkable constancy ; another virus has a similar 

 effect on guinea-pigs. 



Pasteur has already made known the curious fact that he has in 

 his laboratory some dogs that are refractory to the virus of rabies, but 

 he has not till now been able to say whether that was due to their 

 natural constitution or not. He now finds that it is not so, but that 

 he can by a system of inoculations of different kinds, make any num- 

 ber of dogs refractory ; indeed he has now twenty-three. For the 

 present he confines himself to this statement, but it is clearly one of 

 great importance, as man only becomes rabid directly or indirectly 

 from the bite of a dog. He concludes : " Could not human medicine 

 profit by the long duration of the period of incubation to try and estab- 

 lish in this interval of time, before the appearance of the first symptoms 

 of rabies, the refractory condition of subjects that have been bitten ? 

 Much, however, remains to be done before this hope can be realized." 



Yeast-ferments.* — Continuing his researches on the ferment of 

 beer, E. C. Hansen observes that there are in nature a large number 



* Allg. Zeitschr. f. Bierbrauerei u. Malzfabrikat, 1883, p. 871. See Bot 

 Centralbl., xvii. (1884) p. 169. Cf. this Journal, iii. (1883) p. 252. 



