286 PROGRESS OF SCIENCE IN THE CENTURY. 



apart from corporeal affairs, for, as Verworn notes, 

 Miiller defended even in his examination for the doc- 

 torate the thesis : Psychologus nemo nisi physiologus. 

 But it is interesting to find that this genius who did 

 so much to give physiology its modern aspect was like 

 most of his contemporaries, a vitalist. He main- 

 tained that the functions of the body exhibited se- 

 quences comparable to those observed by the chemist 

 and physicist in not-living bodies, yet he believed that 

 there was in the organism a " vital force " which had 

 to be taken account of in physiology. 



Meanwhile pursuing the general trend of biologi- 

 cal research, we may note that just as the study of 

 the intact organism as a bundle of habits and tem- 

 peraments more or less kept in order by a " spiritus 

 rector " gave place to a study of the activities of par- 

 ticular organs the brain, the heart, the lungs, the 

 liver, and so on, so the resulting conception of the 

 living creature as an engine of many parts had to 

 be supplemented by the study of the properties of 

 tissues (muscular, nervous, glandular, and so on), 

 a step which we particularly associate with the pub- 

 lication of Bichat's Anatomie Generale in 1801. 

 Gradually, however, as the microscope was im- 

 proved, the existence and importance of the little 

 areas of living matter which we (unfortunately) 

 call cells was recognised, and in 1838-39 Schwann 

 and Schleiden formulated their " Cell-Theory " or 

 Cell-Doctrine, (a) that all plants and animals have 

 a cellular structure, (&) that the life of all multi- 

 cellular organisms (reproduced in the ordinary way) 

 begins in a single cell the fertilised ovum which 

 proceeds to build up the body by a process of cell- 

 division, and (c} that the life of the whole is ex- 

 pressible in terms of the activities of its component 



