in the intestine of the tadpole . 30 g 
In milk, the caseous part, or curd, corresponds to the albu- 
minous part of yelk, as the butter in milk does to the other 
part or oil of th^^lk. t The principal difference, therefore, 
between milk and^elk is, that the former is in a dilute, and 
the latter in a concentrated state. Hence, Mr. Hatchett ob- 
serves, it appear that many of the oviparous animals dur- 
ing the period of incpbation, are nourished by a pabulum simi- 
lar in quality to that by which young viviparous animals are 
supported, whilst the great degree of concentration of this 
pabulum in the first case is essentially necessary, in order 
that the quantity of nutritious matter which is required during 
incubation, and which is included with the animal within the 
egg, should be condensed into the smallest possible bulk. 
Young viviparous animals are at first incapable of support- 
ing themselves by those substances which are afterwards to 
become their food, and they are therefore nourished for a 
certain period of time by the milk of their mothers ; but 
young oviparous animal^, such as the chicken, partridge, and 
birds in general, come forth from the shells complete in their 
bodily faculties, and immediately partake of the food tp which 
the parent birds are accustomed, so that it seems they are pre- 
pared for this, and are nourished during incqbajtiopi t by a sub- 
stance similar in l lWf MW® 
animals are supported, or suckled, during a certain time after 
their birth, and that the process corresponding to that of suck* 
ling, is, with regard to birds, performed and completed in the 
course of incubation^ j }J(X j b ( 
The experiments which Mr. Hatchett has made upon the 
ova of these different tribes of animals, lead to the conclusion, 
that in all ova, the embryos of which have bones, there is a 
S s 2 
