1838. HOUSE—No. 72. 23 
an acid is generated. But the formation of butter, or its separation 
from the other elements of cream, does not depend on the absorption 
of oxygen gas, as it can be obtained when the atmosphere is entirely 
excluded. The curd which is formed, soon after the separation of 
the cream, becomes a sort of coagulum, by the action of a free acid, 
or by rennet. It is considered as pure caseous matter, or the basis 
of cheese. The action of rennet, in separating the caseous matter, 
is not well understood, but it is generally supposed to act in conse- 
quence of the presence of gastric juice, which is always more or less 
acid. 
Caseous matter yields, on analysis, carbon 59.78, hydrogen 7.42, 
oxygen 11.40, nitrogen 21.38. When burnt, it yields an ash which 
amounts to 6.5 of its weight, the greater part of which is phosphate 
of lime. This substance makes the caseous matter so valuable as an 
article of food to young animals. It is during this period that the 
bones require the deposition of this solid earthy matter to give them 
strength and consistence. Milk, when deprived of cream, has a 
specific gravity of 1.03, and yields, in the 1000 parts, water 
928.75, caseous matter 28, sugar of milk 35, muriate and phosphate 
of potassa 1.95, with traces of a few other unimportant elements. 
The following concise description of a few of the rarer animals of 
this state, is offered in the room of ageneral catalogue. This course 
appeared the most expedient, as two editions of the Geological Re- 
ports have been distributed in all the towns in the state, containing 
catalogues of the animals nearly complete, and in which very few 
additions or alterations can be made at the present time. 
1. Hysrrrx. 
Generic Characters. ‘Teeth. Incisors es canines ae molars 
8 
3 Total 20. 
H. dorsata, Gmelin. Porcupine. Color black. Feet armed 
with long and moderately curved nails, 4 on the anterior, and 5 on 
the posterior feet. Body and extremities covered with coarse hair, 
