84 Anatomy and Physiology of the Mammary Gland. 



a sow with sixteen or even eighteen will only bring forth five or 

 six young- ones ! Nevertheless, it is highly important for success 

 in breeding that the largest number of young should be amply, 

 provided for, or many will be lost for want of sufficient nourish- 

 ment obtainable from their parent. 



Even with the cow the existence of four mammary glands 

 may be taken as evidence that this animal could rear an equal 

 number of calves, if perchance so many should be brought 

 forth at a birth. Indeed it is a practice with some persons 

 on dairy farms to place four calves, which are intended for 

 weaning, upon a cow very shortly after she has been delivered, 

 and to allow them access to her morning and evening. Within 

 a week or two these young animals will, in the interim be- 

 tween their sucking, begin to take a little meal, oil-cake, or 

 soft hay, and also to sip some hay-tea ; and by the time they are 

 ten or twelve weeks old, they are frequently fit to be entirely 

 removed from the cow. Their place is then supplied by two 

 or three others, depending on the quantity of milk yielded by the 

 animal, and these are managed prec isely in the same way until 

 they also can be taken away. Again a third lot of two or three 

 are dealt with in the same manner. In this way ten calves can 

 be weaned within a few months from one cow ; and we are familiar 

 with an instance of forty calves having been thus reared, by an 

 agriculturist of high reputation, from four cows within the past 

 year. It is a practice also which we ourselves have recently 

 adopted, and with perfect success. With such facts before us, 

 it cannot be questioned that in a state of nature as well as in 

 domestication, a cow could sufficiently provide for the susten- 

 ance of four young ones, and this because, as has been stated, 

 she has four distinct mammary glands. 



Notwithstanding the diversity which obtains both with regard 

 to the number and position of the mammae, the secretion of 

 milk is effected in the same manner in all animals. The milk 

 ducts, however, as well as other structures which enter into the 

 composition of these glands, are liable to vary as to the pre- 

 cise manner of their arrangement in different classes of animals. 

 Thus we find that in graminivorous, and particularly in ruminant 

 animals, the lactiferous ducts in tlieir course towards the teat 

 dilate into pouches, capable of containing several ounces of milk, 

 to which the term of reservoirs has been applied. On laying open 

 a gland of this description, these receptacles give an appearance 

 of the organ being chiefly made up of a cell-like structure, the 

 walls of wliich are seemingl}' formed of condensed areolar tissue 

 of varying thickness, but which in reality are found, on close 

 investigation, to consist principally of small lactiferous ducts. In 

 the subjoined engraving, which represents a vertical section of 



