510 PROCESSES INFERRED FROM INDIRECT OBSERVATION 



during the adolescent growth-cycle is the formation of Connective 

 Tissues 1 and if the development of certain of these be retarded in the 

 manner indicated, it may readily be understood how the rate of growth 

 of the animal as a whole, estimated by its weight, is retarded although 

 the growth of its parenchymatous tissues may be considerably acceler- 

 ated. That this is probably the correct interpretation of the facts is 

 furthermore shown by the effect of discontinuing the administration of 

 tethelin to mice after the initial retardation of growth has become well 

 marked. The secondary acceleration of growth which succeeds the 

 retardation in animals which received tethelin, cholesterol or pituitary 

 tissue throughout their lives is, in this event very much enhanced, so 

 that the effect of the initial retardation of growth is not only fully 



FIG. 44. Showing the effect of a brief period (five weeks) of administration of tethe- 

 lin upon the subsequent growth of mice. Animal on the left (31 grams) is the average 

 tethelin-treated animal at five hundred days. On the right (25 grams) an average 

 normal animal of same age. 



compensated, but a supernormal accretion of weight occurs, carrying 



the animals far beyond the average of normal animals of the same age. 



This is strikingly shown in the preceding photograph (Fig. 44), in which 



a female mouse of average normal weight at five hundred days of age 



= 25 grams) is compared with a female representing the average weight 



= 33 grams) of animals which had received four milligrams of Tethelin 



daily from the fifth to the thirteenth week of age; the administrations 



being then discontinued. The remarkable overgrowth which is thus" 



attained is evident even in the average animal displayed in the photo- 



1 Tims BischolT (Volt's Handbuch der Physiologic, Bd. 0, p. .511) finds that the 

 muscular, skeletal and fatty tissues comprise 76 per cent, of the weight of the adult 



W AttJt 8 ' Cent '. f the W6ight f the newborn - Rubner estimates that a man 

 08 contains 37.8 kilos of cell mass of which 40 per cent, is muscular tissue 



