OP THE ASS AND BIRD. 199 



ova, and she brought forth nine pigs, being three more than her sister's 

 first litter. The second time she had only six pigs, being two fewer than 

 her spayed sister. The third time she had eight ; the fourth litter, 

 December 1781, was of thirteen pigs; the fifth litter, June 18th, 1782, was 

 of ten pigs ; the sixth litter, December 6th, 1782, was of sixteen pigs 1 . 



Experiment on an Ass. 



Op. Friday, the 2nd of October, 1789, the ass took the male, and I 

 killed her on the Tuesday following, about seven in the morning, 

 making in all what is called four days, but only ninety-two hours. The 

 uterus was immediately taken out, and it was observed that one ovarium 

 was much larger than the other. It was injected on both sides, and by 

 both veins and arteries. When injected, the increased ovarium was 

 much redder than the other, as also was the horn of the uterus on that 

 side. I cut through the small ovarium first, to see if it led to the 

 better exposing of the other which was in a line. 



I then slowly divided the other, in which I cut across several small 

 hydatids [ovisacs ?], but I came to a glandular substance distinct from 

 the surrounding parts in structure ; and, dividing that, along with the 

 other parts, I came to a kind of cavity in which there seemed to be a 

 kind of fine and loose cellular membrane, in the centre of which was a 

 small rounded body, which was a little bag ; for in dividing this part, I 

 had cut off a little of the side of the bag, into which hole a small 

 globule of air had entered. "Within this was an oblong body, which, 

 when taken out, looked like a little coagulable lymph. 



The secondines of a mare and an ass are the same. The urachus in 

 the foetus of a mare and in that of an ass is a small canal, which passes 

 along the [umbihcal] cord, and opens [into the allantois] between the 

 amnios and chorion, which membranes do not adhere anywhere; so that 

 the urine must lie between those two membranes. 



" ON THE PROGRESS AND PECULIARITIES OF THE CHICK. 2 



Of the Egg of the Bird. 



To understand the progress of incubation, it is necessary we should 

 first understand the anatomy or structure of an egg ; and as it is in 



1 [See Animal Economy, p. 50, for further experiments on the effect of extirpating 

 one ovarium on the number of young produced.] 



2 [This MS. has been printed, with my annotations, in the concluding volume of 

 the ' Physiological Catalogue,' 4to. 1840. The original was not taken possession of 

 by Home, in 1799. and remains in the Archives of the Royal College of Surgeons.] 



