460 SUMMARY OF CURRENT RESEARCHES RELATING TO 



room and warm-room mice have been found to differ from one another 

 in various characteristic respects, provided that the parents were 

 influenced by the temperature conditions from a very early age, it does 

 not appear that these differences in the offspring are entirely parallel to 

 those produced in the parents. There is no proof that temperature 

 conditions which acted on the pregnant mothers determined modifica- 

 tions among the offspring. 



Some correlations were determined. Even when animals of the same 

 history and the same size are considered ; individuals with longer tails 

 have, as a rule, longer ears and feet, are heavier, and have more hair. 



Certain phenomena of growth were noted. After the initial retarda- 

 tion of the cold-room animals in respect to tail length, the tails grew 

 faster, both relatively and absolutely, than those of the warm-room 

 animals. In both lots, the shorter tails grew, on the average, faster 

 than the longer ones. There is a tendency toward compensation in 

 growth, such as was observed by Minot for the weight of guinea-pigs. 



Effect of Castration on Growth.* — Shinkishi Hatai has experi- 

 mented with albino rays to test the effect of the removal of the sex 

 glands in either sex, which he calls gonadectomy. The use of this 

 term as applicable to both sexes leaves castration to apply to the opera- 

 tion on the male, while that on the female is designated by spaying. 

 Five operations were performed : total gonadectomy (castration and 

 spaying), partial gonadectomy (semi-castration and semi-spaying), liga- 

 ture of the spermatic cord, removal of one ovary followed by an isolation 

 of the other from the uterus, and the isolation of both ovaries from the 

 uterus. 



The body lengths were slightly less in all the rats operated on, except 

 the spayed females, in which the body lengths were distinctly greater. 

 The tail length with respect to the body length tends to be slightly 

 longer in the castrated males. The body weight in respect to body 

 length is greater in nearly all rats operated on, but especially in the 

 spayed rats. In castrated and spayed rats the bones (femur, tibia, 

 fibula, humerus, radius, and ulna) tend to be very slightly longer and 

 heavier than in the corresponding controls, and the percentage of water 

 in the bones slightly higher. No characteristic response was observed 

 for the central nervous system. 



In the semi-spayed series the compensatory growth of the remaining 

 ovary is almost perfect as it attains nearly twice its normal size. In the 

 semi-castrated the remaining testis showed an increase of 14 p.c, but 

 this may be solely in the interstitial tissue. The isolated ovaries 

 survived and grew as if they had been connected with the uterus. In 

 the case of isolation of the ovary followed by semi-spaying, the remaining 

 isolated ovary hypertrophies in the same manner as that of the semi- 

 spayed rat. The ligation of the spermatic cord may cause a complete 

 atrophy of the testes and alterations of somatic characters similar to 

 those in castrated rats. No definite conclusions could be drawn in 

 reference to the thyroid gland, which is very variable in weight. 



* Journ. Exper. Zool., xviii. (1915) pp. 1-67. 



