i: I:L. \TION TO i N KKCTIO rs IUSKASKS. 99 



s 'Tx-ation will IM- nn-ded before he can tell where ami when 

 this hinl is a<vustome<l to build its DCS), upon what insects, 

 grains, and berries it feeds, with what other species of birds 

 it lives in peace and with what it is at war. A much 

 greater range of observation and study is necessary Wore 

 the naturalist can tell how his newly discovered species 

 would thrive if carried to a new climate, where it woidd 

 he compelled to live upon unaccustomed food, to build its 

 nest of strange material, ami to encounter new foes. 



We repeat that it is no discredit to the science nor to the 

 men who have developed it to say that the study of bac- 

 teriology has hitherto l>een almost wholly morphological. 

 Without the morphologist the physiologist and the physio- 

 logical chemist could not exist. The science having had 

 for its support only morphological studies, the deductions 

 and formulated statements arrived at by its students have 

 Urn reached in am)rdance with the Knowledge obtained 

 from this source. But now, it being admitted that the 

 causal relation between a given germ and a certain disease 

 is dependent upon the chemical products of the growth of 

 the germ, the fundamental lines of work must IK; altered in 

 order to correspond with this new knowledge. 



The study of the chemical factors in the causation of the 

 infectious diseases opens up for us a field in which much 

 work must l>e done. Let us attempt a statement of the 

 nature of some of the researches that must be carried out 

 along this line. 



In the first place, we must ascertain what germs are toxi- 

 eogenie. This would necessitate a chemical study of all kinds 

 of bacteria, l>oth the pathogenic and the non-pathogenic. 

 Kvery fact ascertained in this investigation will not have 

 its practical application in medicine, but will have its 

 scientific value, and many will most probably l>e of more 

 or less direct service to man. 



Secondly, it must be determined under what conditions 

 these germs are toxicogenic. It is not at all probable that all 

 those bacteria which are capable of producing poisons when 

 grown on dead material outside of the body are also capable 

 of multiplication and the production of the same substances 



