294 



SCIENCE. 



[N. S. Vol. V. No. 112. 



■whose premolars are erupted the surfaces 

 are uneven by the processes interlocking to 

 fix the symphysis securely. At the same 

 time that this change is announced the in- 

 cisors are coming in place. The second tooth 

 lies at first back of the first and third, so 

 the alveolar region is twice as broad as 

 when a little later all three teeth are in 

 li ne . Thus great activities of the symphysal 

 and alveolar regions are coincident. It 

 is at this stage that the cat is prone to 

 disease at the mentum. In forty-eight 

 examples of adult lower jaws examined 

 from your cabinet, thirty-three showed hy- 

 perostosis of the alveolar region for the 

 incisors, the antero-posterior diameter being 

 5 mm. (a measurement twice that which is 

 normal), with loss of at least one incisor, at 

 a time when the sectorials were but slightly 

 worn, while the jaw in other respects showed 

 fully adult characters. In studying senility 

 we are prepared to find the mentum ex- 

 hibiting frequent changes from the normal. 

 The entire region is often hyperostosed or 

 carious ; the incisors in part or entirely lost, 

 and even the canines loosened or lifted 

 by filling up of the bottoms of their sockets. 

 In this manner a slightly plus physiological 

 activity in the young has prepared the way 

 to variation in adult life and to character- 

 istic changes in old age. In the collection 

 I found seven examples of these changes in 

 very old bones. I am informed by Dr. Burk 

 that, since the greater number of cats used 

 for dissection are not over two years old, the 

 number of senile examples in the collection 

 is probably much less than would be found 

 to be the case if data could be collated from 

 life histories of the species secured under 

 average circumstances. 



It is impossible to say which of the char- 

 acters outlined in the above propositions 

 (save alone Prop. VI.) can be transmitted. 

 It is safe to assert that many of them are 

 sporadic in character, though I do not be- 

 lieve them to be adventitious. 



As the individual nears the time of 

 its own extinction it experiences changes 

 in the composition of its tissues and gross 

 variation in characters. Groups of ani- 

 mals which are also approaching extinc- 

 tion behave in a similar manner. Onto- 

 genetic comparison in the first case should 

 be made with the phyllogenetic comparison 

 in the second as well as with the more efii- 

 cient of their own types. The aged individ- 

 uals of the domesticated Bovidse, for ex- 

 ample, should be compared with all the 

 younger adult individuals of the Aurochs.* 



The senile horse should, in like manner, 

 be studied with the phyllogeny of the group 

 to which it belongs. Since our knowledge 

 of this is relatively precise, I have long 

 thought the comparison would be of ex- 

 ceptional interest. 



The difficulty in procuring material for 

 studies in senility is very great and prob- 

 ably accounts for the slight attention which 

 has been given the subject. I wish in this 

 connection to gratefully acknowledge re- 

 ceipt of specimens from Professor Burt 

 Gr. Wilder, Cornell University, from Dr. 

 Charles Burk, University of Pennsylvania, 

 and from Messrs. F. W. True and F. A. 

 Lucas, of the U. S. National Museum. 

 I respectfully solicit additional material 

 from those who do not object to having 

 their cats, dogs and other animals used for 

 scientific study after they have ended hon- 

 orable careers as household pets. 



Hakrison Allen. 

 Philadelphia, Pa. 



*G. S. Miller, Jr. (Science, November 20, 1896, 

 744), in abridging Biichner's account of the degen- 

 erate and lingering European bison herd, speaks of 

 the prevalence of abnormal conditions in parts of the 

 skeleton. According to the tenets of the above essay, 

 these conditions will yield, when studied, the best 

 results when compared with those found in other 

 vigorous groups of genera of the Bovidse, as also with 

 effects of age and disease in the life history of an in- 

 dividual of any one of the species. 



