ON THE ANTITOXINS OF DIPHTHERIA. 



AT the present time there can be no question as to the 

 nature and value of the connection between the 

 biological sciences and applied medicine. Experimental 

 science, which in its infancy advanced along lines widely 

 separated from medicine, has now become closely associated 

 with this, and to an extent impossible for any one to have 

 predicted a quarter of a century ago. This is especi- 

 ally evident in considering the present state of preventive 

 medicine, which is often erroneously held to have been 

 developed by purely legislative measures, while the exten- 

 sive researches carried out in the laboratory that have 

 really create^ the subject are often altogether ignored. 

 Inquiries into the exciting causes of infective diseases can 

 be carried out by methodical investigations in a given dis- 

 trict, or by experimental researches, and the latter, beyond 

 doubt, has proved a more fruitful source of knowledge, 

 since the abundant evidence that many diseases are directly 

 caused by bacteria has been acquired by laboratory work. 



A study of the etiology or causes of disease must of 

 necessity bring the inquirer face to face with a problem 

 which is as old as the history of medicine itself. It is a 

 matter of common observation that certain diseases attack 

 certain individuals, and leave others unharmed. The ex- 

 pression of this in its widest sense is found in the concep- 

 tions of susceptibility and immunity. If the latter state is 

 transferable from one organism to another, then it is 

 obvious that the former may be entirely abolished, and a 

 measure of this nature may be termed prophylactic. If, on the 

 other hand, a disease already developed is arrested in its 

 progress by a similar experiment, then a directly curative 

 principle is involved. The future of preventive medicine, 

 at any rate from the bacteriological view, lies in solving the 

 problem of immunity, and this has now entered upon a 

 stage of great interest. Among infective diseases diph- 

 theria has recently attracted considerable attention, since 



