CHANGES IN THE OVUM. 



117 



certain quantities towards the end of gestation, and is found in the liquor 

 amnii, which owes its yellow color to its presence ; it is swallowed with 

 this fluid, and is then observed in small masses in the stomach. 



The liver appears to be engaged, during foetal life, in the depuration 

 of the blood, as appears from this accumulation of meconium, which is 

 chiefly altered bile ; but at the same time, as has been stated, it is serv- 

 ing as a blood-making organ, and this is probably its principal function 

 before birth. 



The secretion of urine is somewhat active during intra-uterine life, and 

 appears to be effected by the Wolffian bodies before the kidneys begin to 

 act. It is not, however, until the end of gestation that a notable quantity 

 of urine is found in the bladder, and urea in the allantoic fluid of the 

 Cow. It is certain, however, that this fluid is not altogether the urine 

 of the foetus, as its proportion is relatively larger at an early epoch of 

 foetal life, and the communication between the bladder and allantois is 

 more limited towards parturition. 



With regard to the function of the thyroid and thymus " glands," as 

 they have been termed, and the spleen and supra-renal capsules, during 

 foetal life, there is but little positively known. It appears, however, to be 

 admitted that the office performed by these ductless or vascular glands, 

 is to restore to the circulating current any substances which they may 

 withdraw from it, and that their action is subsidiary to the process of 

 sanguification \ being exercised, perhaps, chiefly upon that portion of the 

 nutrient materials which did not pass through the absorbent system when 

 first introduced, but was taken up directly by the blood-vessels. 



SECTION VI. WEIGHT AND DIMENSIONS OF THE FCETUS AT BIRTH. 



The various phenomena connected with development having been 

 completed, so far as uterine existence is concerned, it may be useful to 

 note what has been ascertained with regard to the weight and dimensions 

 of the foetus at birth; the latter being of much importance from an 

 obstetrical point of view, though it is a subject which has not received all 

 the attention it merits from veterinary obstetrists. 



With regard to weight, we find, as might be expected, that this varies 

 considerably, according to the size, breed, and condition of the parents, 

 and other circumstances which more or less influence growth. 



For the Horse species, Boussingault estimated that foals from pa- 

 rents weighing from 400 to 500 kilogrammes, weighed at birth 51 kilo- 

 grammes.* According to a table drawn up by Saint-Cyr, it appears that 

 a foal at birth may vary in weight from 30 to 60 kilogrammes, according 

 to breed and individual peculiarities ; though between 38 to 42 kilo- 

 grammes may be accepted as the average weight. 



With regard to the Bovine species, Tisserant has stated that calves 

 weigh at birth from one-thirteenth to one-sixteenth of the weight of the 

 Cow ; whereas Riedesel gives it as one-tenth. Magne mentions that 

 calves vary between 20, 25, 45, and 50 kilogrammes. Saint-Cyr alludes 

 to the observations made at the Agricultural School of Saulsie, France, 

 where Cows of the Ayrshire breed were chiefly kept. The animals were 

 maintained in good condition all the year round, and though they were 

 only middle-sized, their weight varied between 400 and 650 kilogrammes. 

 The Cows were regularly weighed, as were the calves immediately after 



* The kilogramme is equal to 2*205 pounds avoirdupois. 



