Page:Proceedings of the Royal Society of London Vol 1.djvu/73

Rh appear in each jaw, but that the further progress of these could not be observed, none of the specimens the author has had opportunities of inspecting, appearing to be more than seven years old.

Mr. Home proceeds next to observe, that the elephant, the Sus æthiopicus, and the wild boar, are the only recent animals in which he has hitherto met with so extensive a masticating surface of the grinding teeth; the human species only excepted, in which the mode of dentition is somewhat upon the same principle as that of the wild boar, with this difference, that the hindmost teeth, called, from the late period of life at which they cut the gum, Dentes Sapientiae, do not exceed the others in size, and have often not sufficient room in the jaw to come into their regular place. A conjecture is hence de rived, that when the period of man's life was longer than it is at present, the growth of the posterior part of the jaw was continued for a greater length of time, so as not only to make room for the present, but perhaps also to admit of a succession of a still greater number of additional grinders.

Upon comparing the grinders of the boar with the large fossil teeth found on the banks of the Ohio, they were found so much alike, both in their external appearance and internal structure, as to render it more than probable that they are teeth of the same kind, only dif- fering in size. Not so, however, those of the fossil skeleton some time since found in South America, and described by M. Cuvier. These were found so unlike those of the boar, or the above-men- tioned incognitum, as to leave no doubt of its being an animal of a different genus. From the progressive mode of dentition above described, it is in ferred, that the animals to which it appears to be peculiar, have by nature been intended for great longevity. This we know to be the case in the elephant: and though opportunities have not yet offered for ascertaining the term of life of the wild boar, some quotations from ancient authors are here adduced, which indicate that boars of enormous size have at different times existed; whence the proba bility is inferred that their bulk must have been the growth of many years.

The author prefaces his paper by declaring that the cause of the ascent of the sap in trees appearing to him not to have been as yet satisfactorily accounted for, he resolved to enter on an experimental inquiry on the subject; and that having met with some facts of which he had found no mention in any author, he flattered himself an account of them might not be unacceptable to the Society

The first experiments were made with a view to determine whether the sap does actually, as has been thought by some, ascend along