82 Anatomy and Fhysiology of the Maiitmary Gland. 



of the mammary gland, as developed in some other animals 

 besides those of the Ox tribe, as thereby a better illustration 

 will be afforded of the precise arrangement of its component 

 parts in the cow. 



The mere existence of these glands shows that the creature 

 which possesses them belongs to the higher order of animated 

 nature, no matter what may be its size or form, the cliaracter 

 of its food, the region it inhabits, or the medium in which it 

 lives. Mammalian animals, so called from rnavima, a teat, have 

 consequently certain properties which are common to them all ; 

 thus, not only have they an internal skeleton, the spine of which 

 is composed of different segments — vertehrce — constituting them 

 vertebrated creatures, in contradistinction to others that have no 

 such skeleton — the invertehrata — but they are likewise warm- 

 blooded, have blood of a red colour and a double circulation. 

 They also breathe atmospheric air, possessing for this purpose 

 lungs which aerify their blood for the maintenance of vitality ; 

 their bodies for the most part are covered with hair or wool, .'md 

 their young are developed in an internal organ — the womb — and 

 when brought forth are nourished for a time by the secretion 

 afforded by the mammary glands of the parent, until they are old 

 enough to seek their own food or have it supplied through other 

 sources. 



Without entering into the subject of the classification of mam- 

 malian animals, or the rules appertaining thereto, it will be 

 sufficient for our purpose to observe that each is admirably 

 adapted, by a modification of its several organs, for the position 

 it has to occu])y, as well as for the obtainment of the food on 

 \\ hich it has to subsist. By far the greater part of mammals are 

 designed to be inhabitants of the land ; not a few, however, dwell 

 in the water, and some may be said to occupy the air. Examples 

 of the two latter are to be found in whales, dolphins, porpoises, 

 ifec, which dwell in the mighty deep ; and in bats, those winged 

 creatures that flit through the dusky air. Of the d(jlphins it has 

 been said that the female brings forth but a single one at a birth, 

 which she nurses and suckles with the greatest care. Bell, in his 

 admirable work on British Quadrupeds, writes that "the mammary 

 glands of the dolphin at the period of birth become enlarged, 

 and the teats exsertcd : the young one seizes the teat with its 

 lips, and the mother lies in some degree on one side in order to 

 enable both herself and her young one to respire whilst the 

 operation of suckling is going on." Tlie same author likewise, 

 when speaking of the peculiarities of bats, says that " the female 

 bat brings forth one or two at a birth, which she nurses with 

 great tenderness and care, carrying it about with her, and holding- 

 it enshrouded in her ample cloak, Avhich preserves it from all 



