(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Biodiversity Heritage Library | Children's Library | Advanced Microdevices Manuals | Linear Circuits Manuals | Supertex Manuals | Sundry Manuals | Echelon Manuals | RCA Manuals | National Semiconductor Manuals | Hewlett Packard Manuals | Signetics Manuals | Fluke Manuals | Datel Manuals | Intersil Manuals | Zilog Manuals | Maxim Manuals | Dallas Semiconductor Manuals | Temperature Manuals | SGS Manuals | Quantum Electronics Manuals | STDBus Manuals | Texas Instruments Manuals | IBM Microsoft Manuals | Grammar Analysis | Harris Manuals | Arrow Manuals | Monolithic Memories Manuals | Intel Manuals | Fault Tolerance Manuals | Johns Hopkins University Commencement | PHOIBLE Online | International Rectifier Manuals | Rectifiers scrs Triacs Manuals | Standard Microsystems Manuals | Additional Collections | Control PID Fuzzy Logic Manuals | Densitron Manuals | Philips Manuals | The Andhra Pradesh Legislative Assembly Debates | Linear Technologies Manuals | Cermetek Manuals | Miscellaneous Manuals | Hitachi Manuals | The Video Box | Communication Manuals | Scenix Manuals | Motorola Manuals | Agilent Manuals
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Observations on the Structure, and Mode of Growth, of the Grinding Teeth of the Wild Boar, and Animal Incognitum."

52 

trary, punctures, dimples, and a poor appearance of the luminous 
clouds,. the absence of ridges, nodules, large openings, and flats, de- 
note a spare emission of heat, and may induce us to expect severe 
seasons. 

Pursuing this last idea, Dr. Herschel subjoins, at the end of his 
paper, a comparative view of the best accounts that are to be met 
•with of the appearances of the sun at particular periods as far back 
as the middle of the seventeenth century, with the state of the sea- 
sons during the same periods. Of the latter, the best information 
could only be gathered from the state of vegetation, particularly of 
com, of the price of which registers have been kept many years back : 
and though this price be by no means an accurate criterion of the 
quantity of corn produced, yet it is recurred to as the least objec- 
tionable that could be obtained. The result of this review actually 
leads to the conclusion, that the price of wheat has constantly risen 
during the time the sun has been without spots ; and that it has 
always fallen when those spots began to re- appear. 

The Doctor seems aware of some fallacy in this mode of argumen- 
tation; but he adds some hints by which several of the objections 
might, he thinks, be obviated. 

Observations on the Structure, and Mode of Growth, of the grinding 
Teeth of the Wild Boar, and Animal incognitum. By Everard 
Home, Esq. F.R.B, Read May 7, 1801. [Phil Trans. 1801, 
1^.319.3 

The author on a former occasion laid before the Society aii account 
of certain peculiarities in the growth of the grinding teeth of the 
Sus sethiopicus, and pointed out the similarity of their structure to 
that of the elephant. Having since discovered that alike resemblance 
extends also to the dentition of the wild boar, though in a less de- 
gree, and at a later period of life, he Is pleased to communicate to 
the Society, in his present paper, some further remarks on this cu- 
rious subject. 

We here learn, that in the species of the Sus, the first or tempo- 
rary grinders are sixteen in number ; viz. four in each side of the 
upper, and as many in the under jaw ; that these are shed in the usual 
manner ; and that their places are supplied by larger teeth, rising 
from the substance of the jaw, immediately under the old ones ; 
that before these first teeth are shed, one of the more permanent 
grinders is formed in the posterior part of each jaw, which, although 
it be in its place with the first set, is yet to be considered as belong- 
ing to the second ; that besides these five teeth, the rudiments of a 
sixth are farmed in each jaw, which afterwards grows larger than the 
preceding ones, the jaw increasing in size, so as to make room for 
this as the posterior grinder ; that this tooth, when perfect, is double 
the size of , the other grinders, its masticating surface having eight 
fangs, BO that |t very much resembles two large grinding teeth in- 
corporated into one ; that, in time, the rudiments of a seventh tooth 



5S 

appear in each jaw, but that the further progi'ess 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 
sethiopicus, 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 Sapientise, 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. 

Account of some Experiments on the Ascent of the Sap in Trees. In a 
Letter from Thomas Andrew Knight, Esq. to the Right Hon, Sir 
Joseph Banks, Bart. K,B. PM.S, Read May 14, 1801. {PhiL 
Trans. 1801,^9.333.] 

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