OF 
vs 
1886.] i The Mammary Gland of the Eiephant. | 929 
_ tnough in the present, but rendered far more so by the lapse of 
time. Action and reaction between organism and environment ; 
the demands of increasing functional activity upon plastic tissue, 
and the effects of use and disuse, these are the fundamental prin- 
ciples involved, and we can only surmise at the primitive condi- 
tion of affairs from the few tangible points presented to us. By 
attention to the following facts we may be able to gain a few ideas 
which will possibly throw some light upon the subject. At the 
anterior end of the great arterial trunk (aorta) two branches arise 
(subclavian) which proceed to the fore limbs. These, in turn, 
give off each a branch (internal mammary) which passes down- 
-ward and backward along the anterior thoracic wall. At the pos- 
= terior end of this great trunk two other branches arise (diac), 
Proceeding to the hind limbs, these also giving off each an artery 
(superficial epigastric) which runs forward in the abdominal wall 
to anastomose with the terminal branches of the internal mam- 
Mary, thus forming an arc on each side of the ventral median’ 
-line from neck to groin. This we will call the mammary arc. 
Now it is evident that in those mammals whose glands are situ- 
ated solely in the pectoral region, as in Primates, Chiroptera, ele- 
_ Phant, etc., the internal mammary artery is the main supply of 
the gland ; while in those in which the structure is inguinal, as in 
s horse, deer, etc., the superficial epigastric is the main blood 
ieder, 
] a 
an 
‘Surface of the body, as in Carnivora, Suidz, etcs the entire arc 
of blood- vessels comes into play as a source of supply. We- 
nave every reason to believe that this latter state of affairs was 
the original arrangement of the parts, as the lowest and most 
y 
Imitive condition. As specialization proceeded a reduction in 
the young animal, while the rest atrophied and finally disap- 
h Again, when the glands are situated in a row along the under 
_ phosis and nutrition in their broadest sense; a study vague 
ancient forms now extant present this same condition correlated i Oe 
with plurality of young at a birth, which is also undoubtedly a ` 
pri i x 
the number of young at a birth followed, and consequently fewer : > ; 
nds were used ; those only which were the’ most convenient a 
peared from want of use. Whether the prototype of the Pro- ` 
‘i $ idians was large or small, whether it produced a number of | as 
ig at a single birth, and consequently possessed a series DE. 
running along the belly, or what its habits were we cannot _ 
