On the relation between the thymus and the generative organs and the influence of these organs upon growth

Calzolari was the first to show that in castrated male animals the absolute weight of the thymus is larger than that of the same gland in normal animals. The experiments were made upon six rabbits, which were castrated when between one and three months old and killed at various periods afterwards up to nine months, each rabbit being compared with a control. Subsequently Henderson carried out a statistical investigation upon the weight of the thymus in cattle, and showed that in these animals castration caused a persistent growth and a retarded atrophy of the gland. Henderson also records two experiments upon guinea-pigs by Noël Paton, and the results of these are confirmatory of the observations upon cattle. The possible reciprocal action of the thymus upon the testis was investigated by Noël Paton, who removed the former organ from 24 young, guinea-pigs and killed them when they attained weights varying from 115 to 355 grm. These animals were compared with 23 normal guinea-pigs kept as controls. The conclusion reached was that in guinea-pigs below 300 grm. (i. e., prior to the time when the thymus usually atrophies) thymectomy is followed by a more rapid growth of the testes. In guineapigs above 300 grm. Paton found that the difference in weight of the testes in thymusless and normal animals was not manifest. The figures upon which these conclusions are based are dealt with statistically in an appendix to this paper by Mr. G. Udny Yule.