662 



FUNGI 



first oroke out with violence. It has been shown by microscopic 

 investigation that in silkworms strongly affected with this disease, 

 every tissue and organ in the body is swarming with these minute 

 cylindrical corpuscles about 4'2^u long, and that these even pass into 

 the undeveloped eggs of the female moth, so that the disease is 

 hereditarily transmitted. And it has been further ascertained by 

 the researches of Pasteur that these corpuscles are the active agents 

 in the production of the disease, which is engendered in healthy 

 silkworms by their reception into their bodies ; whilst, if due pre- 

 cautions be taken against their transmission, the malady may be 

 completely exterminated. 



Fl<J. 500. Pure-cultivations on glycerine- agar from human tubercular sputum : 

 a, after six months' growth (fifth sub-culture) ; 6, c, after ten months' growth 

 (fourth sub-culture). (Crookshank.) 



Bacteriology is now so distinctly a branch of biological science 

 that it would be out of place here to present even a summary of its 

 voluminous details and methods of research. The microscope in its 

 most perfect form is an indispensable adjunct to the rapidly progres- 

 sive work of this department of biological research, and the most 

 delicate and refined employment of the microscope and all its 

 adjuncts is in the last degree important. Only a skilled microscopist 

 can be a successful bacteriologist. But for the methods of the 

 bacteriological laboratory we must refer the reader to treatises on 

 this branch of science, 1 it being enough here to remark that the 



1 The English student will find an admirable aid in the Text-book of Bacterio- 

 logy and Infective Diseases (4th ed.), by Professor E. Crookshank. 



