692 A MANUAL OF VETERINARY PHYSIOLOGY 



tion. During the period of * rut ' mature spermatozoa are pro- 

 duced, and probably at no other time. In insectivora and 

 rodents there is a growth of the generative organs, especially the 

 testes, which, if intra-abdominal, may shift position, and appear 

 externally. In the hedgehog appendages like the seminal vesicles 

 assume remarkable proportions in their capacity as secretory 

 organs, shrinking to normal when the period of excitement has 

 passed away. 



Cause of Rutting.- — There would appear to be little doubt that 

 1 rutting ' is due to an internal secretion of the testicle, in all 

 probability elaborated by the interstitial rather than the sperma- 

 togenetic cells. 



Effect of Removal of Testicles and Ovaries. — The influence of the 

 removal of the ovaries and testicles on general metabolism is a 

 subject which has been referred to in dealing with internal secretions 

 (p. 293), and attention has there been drawn to the fact that both 

 in cats and dogs the complete removal of the ovaries, and, it may 

 be added, of both horns of the uterus, may not in every case prevent 

 an animal exhibiting oestrus. Such, of course, are exceptional cases, 

 for ovariotomy usually suppresses the function. If an animal, for 

 instance, be operated upon before puberty — viz., before an cestrual 

 period has had time to appear — such a one will not subsequently 

 experience any sexual excitement. If the operation be performed 

 during the first pregnancy, the ' heat ' period does not occur. If 

 operated upon after one or more cestrual periods, and not being at 

 the time pregnant, there may be a few returning ' heat ' periods and 

 free sexual intercourse. If castration of the stag be practised, the 

 antlers fall off from the seventh to the ninth day after operation ; 

 fourteen days is said to be the longest time they remain. This is 

 evidence of an internal secretion of the testicle (p. 293), which 

 influences the growth and shedding of the antlers, while the chain 

 of evidence is completed by the fact that castration on one side 

 only affects the growth of the antler on that side. If the epididymis 

 be left after complete castration, its presence modifies the growth 

 of the next pair of antlers.* Similarly, the growth of parts in other 

 male animals is affected by castration. Cats operated upon while 

 very young have heads which are indistinguishable from the female ; 

 the tissues of the jowl, which give the head of the male cat such a 

 massive appearance, are lost after castration, and this may occur 

 even when the operation is performed late in life. Female cats 

 operated upon while young acquire a head of the male type, and 

 even if the operation be performed when approaching middle life, 

 there is a disposition to broadening of the skull (Leeney) . 



The alteration in the shape of the male and female skull observed 

 in the cat when castration or ovariotomy is practised in early life, 

 supports the view advocated by Heape that no being is wholly male 

 or wholly female, but a portion of each sex, with one predominant. 

 Cocks converted into capons when young do not develop such full 

 male plumage, and the combs and wattles are more like those of 

 the hen. Pullets from which the ' clutch ' has been taken grow 

 fat, and sometimes put on male plumage. Hen pheasants injured 



* I am indebted to Mr. H. Leeney, M.R.C.V.S., for these facts and much 

 other information on the subject. 



