THE MICROSCOPE IN J3TIOLOGY. 343 



or may from time to time give rise to changes peculiar to 

 it. Particles of living tubercle may be so minute as to be 

 carried in the atmosphere, although tubercle is not emi- 

 nently contagious. As to cancer germs, many circum- 

 stances render it improbable that they can be transmitted, 

 so that living disease germs differ remarkably in vital 

 power as well as forms of activity. Yet they resemble 

 each other in general appearance. Neither by its form, 

 chemical composition, or other demonstrable properties, 

 can the vaccine germ be distinguished from the small-pox 

 germ, or the pus germ from either. All are like the 

 minute particles of bioplasm of the blood, from which 

 they differ so remarkably in power. Of the conditions 

 under which these germs are produced, and of the manner 

 in which the rapidly multiplying matter acquires its new 

 and marvellous specific powers, we have very much yet 

 to learn. For the manner of detecting these germs in the 

 air, etc., see the former part of the present chapter. Mr. 

 Lister's excellent plan for the antiseptic treatment of 

 wounds, and especially the results of carbolic acid spray 

 in surgical operations, together with many posititive ex- 

 periments, show that carbolic acid has a powerful action 

 in arresting vital phenomena or destroying bioplasm. In 

 its presence embryonic life is impossible ; under its power- 

 ful influence all minute forms of life perish. Dr. Beale, 

 also, refers to the effects of carbolic acid, and sulpho-car- 

 bolates administered internally, in checking the too rapid 

 growth of bioplasm in the blood and tissues, as well as to 

 the importance of disinfectants, or the destruction of dis- 

 ease germs in the air, sewage, etc. 



Among the strongest objections to the theorj r of fungoid 

 disease germs are those given by Dr. Bastian (a strong 

 supporter of spontaneous generation), that the theory de- 

 mands a belief in the existence of organisms never known 

 in their mature state, and whose existence is not demon- 

 strated but merely presumed ; that such germs have been 



