ON THE REPRODUCTIVE SYSTEM IN ANIMALS. 525 
as I can learn, have any nerves been discovered as entering into 
its composition. Hence all the communication that exists between 
the mother and foetus must be carried on by means of the blood 
circulation, the placenta forming the point of attachment and con¬ 
sequent communication, &c. I am well aware that many physi¬ 
ologists maintain that, in the highest species of animals, the blood 
cannot be returned from the foetus to the mother during utero- 
gestation. Whether this be the fact or not, I have not the means 
of proof; but that the blood can be, and is, returned from the foetus 
to the mother in the bovine race, I have no doubt. Had there 
existed in my mind any doubts on the subject, these doubts have 
been set at rest, completely and for "ever, by a case which lately 
occurred in my practice :— 
An Aberdeenshire cow, in calf, and past the ordinary period of 
utero-gestation, from some unknown cause had a slight rupture in 
the left lung. A constant hemorrhage from the fissure proved 
fatal in three days. I carefully removed the uterus, with its 
contents, entire. On cutting it open, the liquor amnii presented 
the usual healthy appearance. All the vessels of chorion, amnion, 
&c., were white, flaccid, and empty. There were not three ounces 
of blood in the animal, taken with all its membranes and placenta. 
Here is undeniable evidence that, in the cow, the organization of 
the placenta admits the return of the venous blood from the foetus 
to the mother; so that, however intricate it may be, the existence 
of a free communication between them is no matter of doubt. If 
a cow, say of the pure Aberdeenshire breed, is in calf to a bull of 
the Short-horn breed (known as the Teeswater breed), in pro¬ 
portion as this calf (foetus) partakes of the nature and physical 
character of the bull, just in proportion will the blood of the cow 
become contaminated, and herself a cross, for ever incapable of 
producing a pure calf of any breed. 
It is maintained, therefore, that the great variety of nondescript 
animals to be met with are the results of the crossing system; the 
prevailing evil of which is the admission of bulls of various breeds 
to the same cow, whereby the blood is completely vitiated. 
Having thus stated the cause , and proved it to be neither a vague 
hypothesis nor a dry speculation, but a plain matter of fact, 
I shall now advert to some of the effects, as proofs of the operation 
of the cause just stated and the proposition laid down. 
SECT. II.— Cases illustrative of the Principles advocated. 
In the records of the Transactions of the Royal Society of 
London for the year 1821, are related the following circum¬ 
stances:—A thorough-bred mare, the property of Sir Gore Ousely, 
