PRESENT PROBLEMS OF PHYSIOLOGY 427 



properly to those sciences whose dominant method is that of obser- 

 vation and comparison. In this regard the history of physiology 

 offers an analogy to that of physics. Most of the problems of astro- 

 nomy and geology are in a wide sense physical problems, but in 

 the division of labor made necessary by the extent of the field to 

 be cultivated, the specialist in physics has limited himself to the 

 study of the properties of inanimate matter so far as they can be 

 approached by the methods of laboratory experiment. The wider 

 relations of this matter to the cosmical processes throughout the 

 visible universe, and its transformations during long periods of 

 time, have formed the subject-matter for independent although 

 related sciences. The astronomer or geologist makes much use of 

 physical knowledge and physical methods, but his subject is large 

 enough to form an independent department of science. A similar 

 division of labor has been followed in the sciences that deal with 

 animate nature, and the part that has fallen to the physiologist 

 is mainly the experimental laboratory study of the properties of 

 living matter. It seems proper, and indeed necessary, that the broader 

 ecological problems should form an independent science which 

 will need specialists of its own. Work of this kind cannot be re- 

 garded as lying within the province of the specialist in physiology, 

 although without doubt the development of the physiological 

 sides of the subject will be made largely through methods and 

 technique borrowed or adapted from physiology, and on the other 

 hand the results obtained from ecological work will doubtless 

 exert a reflex influence upon the methods and especially the the- 

 ories of physiology. 



The matter stands otherwise, however, in regard to the deeply 

 interesting and important facts of embryological development. 

 The laws of growth and senescence, the secrets of fertilization and 

 heredity, must be studied in the long run by the physiologist; they 

 are intrinsically physiological problems and must yield at last 

 to the experimental methods of the laboratory. These questions 

 have been studied heretofore chiefly by anatomical methods; but 

 this is the natural order of development. The anatomical side is 

 the simpler; it precedes and serves as a basis for physiological in- 

 vestigation, as the renaissance of anatomy in the sixteenth cen- 

 tury formed the logical precursor of a similar awakening in physi- 

 ology in the seventeenth century. The anatomist has been forced, 

 so to speak, to take up first the problems of development, but of 

 necessity the need for experimental work has soon made itself 

 felt. The results that have been obtained by the use of the simple 

 but ingenious experiments so far employed have been most sug- 

 gestive, and indicate clearly that a promising future awaits the 

 further extension of this method. If for a time longer such work 



