ZOOLOGY 333 



the century. Although this substance had been casually 

 observed at intervals from 1755 onwards, its true nature 

 was entirely unrecognized. The turning point came 

 when Felix DUJARDIN (1801-1860) experimented with 

 it and distinguished between it and other forms of matter, 

 such as mucus, gum, gelatine, albumen, etc., with which 

 it had superficial resemblance. He designated it "sar- 

 code," recognized it as the physical substratum of life, 

 and in 1835 announced it as a living jelly endowed with 

 all the properties of life. This idea received elaboration 

 from various sources, and, finally, culminated in the 

 demonstration by Max SCHULTZE (1861) of the essential 

 identity of all living substance in plants and animals and 

 now designated protoplasm. This, in combination with 

 the cell theory of SCHWANN, led to the foundation of 

 biology in its modern sense, and Dujardin ranks as the 

 scientific discoverer of protoplasm. 



(3) Germ Theory of Disease. The brilliant work of 

 PASTEUR (1822-1895) belongs to all biology. Starting 

 his scientific career as a chemist, he branched into bio- 

 logical fields, and through his later work came to be 

 recognized as one of the foremost men of biological 

 history. His supreme service was in applying the re- 

 sult of biological investigation to the benefit of man- 

 kind. In laying the foundation of micro-parasitology 

 (about 1875), ne opened a subject that overlaps the 

 different conventional divisions of biology, and his foun- 

 dations have been built upon by botanists, zoologists, 

 and physicians. His investigation gave an immense 

 impulse to the study of pathogenic organisms; and while 

 his researches supplied the foundations of scientific 

 medicine, at the same time they opened investigations 

 in the life-history of micro-organisms that have been so 

 extensively developed by zoologists. 



