PARTURITION— PUERPERIUM— LACTATION 85 



it is said that with castrated cows and goats lactation may con- 

 tinue almost indefinitely, but this is not established. It is 

 noteworthy that there are no secretory nerves supplying the 

 mammary glands, which are therefore in this respect unlike the 

 salivary glands or sweat glands. 



The mammary glands of new-born animals sometimes secrete 

 small quantities of what is known as " witch's milk." This 

 fluid contains most of the constituents of normal milk, but the 

 solid substances are less in amount. 



In all mammals, with the possible exception of the Mono- 

 tremata (platypus, etc.), the milk glands are probably of the 

 nature of modified sebaceous glands. 



Parturition in the Lower Mammals 



The process of parturition in the lower mammals is essentially 

 similar to what it is in man. Its duration varies in the different 

 species. In the mare it takes from five to fifteen minutes, in 

 the cow about two hours, in the sheep fifteen minutes for each 

 lamb born, in the sow, bitch and cat from ten to thirty minutes 

 with sometimes an interval of one hour between each birth. In 

 the Carnivora, the mother usually gnaws through the umbilical 

 cord, but in the other animals it is torn. The placenta may 

 not be got rid of until several hours after the young is born (as 

 in the mare). 



Sometimes, as not infrequently happens in the mare, the 

 young animal is born within the intact membranes, and shoidd 

 be liberated in order to avoid asphyxiation, but more usually a 

 few minutes or more elapse before the placenta is detached and 

 got rid of. Occasionally the membranes are retained in the 

 uterus, where they are hable to become infected with bacteria 

 and set up inflammation ; if they are not discharged steps 

 should be taken to remove them. 



