96 THE SEX-COMPLEX 



Foetal hor- that in certain marsupials the amount of mammary 

 specific! n ° development at each period of ovulation is such that 

 it is difficult to distinguish the condition of the mammae 

 in these circumstances from that associated with 

 pregnancy ; and consequently these authors believe 

 that the stimulus to the mammae comes from the 

 internal secretion of the corpus luteum. Further, as 

 Heape 1 has described, virgin bitches have often been 

 known to suckle puppies successfully; and, as I have 

 myself observed, bitches subsequently to oestrus and 

 without fertilization may have 'milk' in the mammae 

 at the time when parturition would have occurred had 

 they been fertilized. Males, too, are supposed 2 to have 

 performed the function of lactation. 



All these facts go to show that however stimulating 

 the fcetal hormone may be in regard to the mammary 

 activity, which subsequently leads to the secretion of 

 milk, it is neither specific nor essential, for various 

 hormones, mechanical stimuli, and other exciting causes 

 such as pelvic tumours, not infrequently arouse mam- 

 mary activity, even in the absence of pregnancy and 

 parturition. 

 Sensitization It may be stated, therefore, that although the breasts 

 mammse. have a special function connected with conception, which 

 is probably the most powerful stimulus to the prepara- 

 tion of the breast — the sensitization of the mammae, as 

 we may call it — the subsequent flow of milk is merely 

 a diversion of excretion through the sensitized glands. 

 There are, moreover, many sensitizing agents, and 

 many secretory stimulants. 



INFLUENCE OF LACTATION ON THE MATERNAL META- 

 BOLISM AND FUNCTIONS 



Lactation is of benefit to the normal woman, as I 

 shall explain directly. If, however, a woman is unable 



1 Heape, W., Journ. Physiol. {Proc. Physiol Soc.), 1906, vol. 

 xxxiv, p. 1. 



2 Novak, J., Erkranh. des Weiblichen Oenitales Supplemente, 1912, 

 Vol. i, p. 539. 



