624 SYNOPSIS OF VETERINARY CONTINENTAL JOURNALS. 
1. The callus in young birds is formed always much more 
rapidly than in adults and old or sick animals. 
2. Twenty-two hours after a fracture in chickens there is 
a proliferation of the deep parts of the periosteum, and forty- 
six hours after the new formation is already considerable. 
3. Adults present no such characters in this lapse of time. 
4. Seventy-two hours after the fracture of the bones of 
young fowls the callus seems to have acquired its maximum 
hulk. The Haversian canals enclose numerous cellular 
elements. Now commences conversion of connective 
elements into bone. The alteration of the cartilaginous 
cellules commences at forty-six hours, and is completed at 
about the fifth day. 
5. Only the periosteum and the elements in the Haversian 
canals are involved in callus production. 
6. The fibrinous coagulum of the extravasated blood does 
not assist in formation of the callus ; its contact and pressure 
even hinder proliferation of the elements of the periosteum. 
7. The repair of the cracks, which in simple fractures 
almost always occur at the extremities of the fragments, 
results from new formation of Haversian canals and by 
the continuity which is established between those of the 
bone and of the newly-formed tissue. 
8. The callus, which is formed entirely at the extremities 
of the bones, is formed simultaneously by the periosteum and 
by the medullary tissue. 
The author adds that in one case he has still seen cartila¬ 
ginous substance twenty-seven days after fracture. 
Giornale di Anatomia Fisiologici e Pcithologia degli Ani- 
mali, January and February, 1879).— The Ancestors of the 
Horse. —The time is not long past when we thought that the 
original country of the horse was Asia, and that from that 
centre of origination the noble animal became spread over the 
whole world, passing over to America at the time of the dis¬ 
covery and conquest of that continent. Naturalists have al¬ 
ready been obliged to modify their opinions in this matter, and 
it is by no means impossible that the complete genealogical 
tree of the horse will show itself in America. Indeed, Pro¬ 
fessor Marsh, of New Plaven, when exploring the mountains 
of Colorado, has discovered fossils of no less than forty-four 
species of Ungulata, which constitute an uninterrupted tran¬ 
sitional chain passing to the horse. In Europe, we have found 
the Anoplotherium, the Hippoterium, the Palmotherium, 
the Anchitherium, the Hipparion, and Equus fossilis v. 
Fur opens, which exhibit a gradual transition towards the horse 
of the present day, and are all of a greater size than the 
