84 Biology in America 



est importance in our efforts toward the making of a better 

 human race. 



In 1913 this work was taken over by the Carnegie Institu- 

 tion and organized in its Department of Embryology, which 

 was under Professor Mall's direction until his death in 1917, 

 and since then has been conducted by his successor, Dr. Geo. L. 

 Streeter. The work of the department, while not limited to 

 human development, has that as its focal point. 



When Dr. Casper Wistar was teaching anatomy at the Uni- 

 versity of Pennsylvania in the early part of the last century, 

 and discussing with President Jefferson the bones of the mas- 

 todon which the latter had discovered in Shawangunk County, 

 N. y., he little foresaw the institution which the future 

 was to raise upon the foundation he was laying. The col- 

 lection of anatomical specimens which he gathered has since 

 grown into the splendid museum of the Wistar Institute in 

 Philadelphia, founded by Dr. Wistar 's grand-nephew in 1892. 

 While the Institute was established primarily as a home for 

 the W^istar Museum, its usefulness has far outgrown the func- 

 tion of mere display. In research, and especially as a center 

 for dissemination of its results through scientific journals, it 

 tills a place unique in American science. 



While its researches have been largely of a technical char- 

 acter, chiefly upon the nervous system, they form the basis 

 for future investigations, which are likely to prove of the 

 highest importance to man. The rat has been used as the 

 experimental subject for these researches. For this purpose 

 the Institute maintains a rat colony of many thousand 

 individuals, and from April, 1917, to April, 1919, it furnished 

 thirty-five thousand rats to government and other laboratories, 

 or one rat every thirty-five minutes during this period. A 

 comparison of the growth of the body as a whole, of the 

 nervous system and of twenty other organs in rat and man, 

 has shown a general similarity in both animals, if comparison 

 be made at the same relative stage of development in both. 

 The rat grows approximately thirty times as fast as man and 

 lives approximately one-thirtieth as long a life (three years). 

 The rat is weaned at twenty days, man at fifteen months 

 while the development of the nervous system is approximately 

 the same at this age (i.e. when weaned) in both animals. Simi- 

 lar studies, both of the nervous system and of other organs, 

 have given similar results. The rat furthermore is almost as 

 omnivorous as man, and requires much the same food con- 

 stituents to keep him healthy. 



If then the growth of the nervous system in the rat can 

 be increased for example by exercise or retarded by poor 

 food, we may logically expect similar results in man. To 



