344 



PRESENT PROBLEMS IN EVOLUTION AND HEREDITY. 



versely in the degeneration of tue crown, disnse foreshadows atrophy 

 and diaapi)earance. 



Upon the whole, witli some exceptions which we do not at pi-esent 

 understand, the course of evolution of the teeth supports the evi- 

 dence derived from the skeleton that, whether any true causal relation 

 has existed or not, the lines of individual transformatiou in the Avhole 

 fossil series preceded those of race transformation. 



Evolution of the htman upper jiolars.— Diiij^ram 9 — Anaptomorphiis, a Lowor Eocene monkey. 

 Diafcraiii in. — An I'pper Koceiie monkey. LMajiraiiis 11 and 12. — Human; 11, E.sqnimaiix; 12, nejiio. 

 Sec addition of ■■talon," hi/, to --tri^on '' composed of j(«, ;;*/•, me. 



The rise of new organs. — We owe to Dr. Arbuthnot Lane a most 

 interesting series of studies upon the intiuences of various occupa- 

 tions upon the human body. He proves conclusively that individual 

 adaptation not only i)roduces profound modifications in the ])ro])ortions 

 of the various parts, but gives rise to entirely new structures. 



His anatomy and physiology of a shoemaker* shows that the life-long 

 habits of this laborious trade produce a distinct type, which if ex- 

 amined by any zoological standard would be unhesitatingly pro- 

 nounced a new species — homo sartorius. The psychological analysis 

 wdiicli a Dickens or Balzac would draw, showing the influences of the 

 struggle for existence upon the spirit of this little tailor, could not be 

 more pathetic than Dr. Lane's analysis of his body. The bent form, 

 crossed legs, thumb and forefinger action, and peculiar jerk of the 

 head while drawing the thread, are the main features of sartorial habit. 

 The following are only a few of the results: The muscles feuded to 

 recede into tendons, and the bony surfaces into which they were in- 

 serted tended to grow in the direction of the traction which the 

 nniscle exerted upon them. The articulation between the steriuim and 

 the clavicle was converted into a very complex arthrodial joint, con- 

 stituting almost a, ginglymoid articulation. The sixth ])air of ribs 

 were anchylosed to the bodies of the vertebne, indicating that they 

 had ceased to rise and fall with sternal breathing, and that respira- 

 tion was almost exclusively diaphragmatic. The region of the head 

 and first two vertebra' of the neck was still more striking: the trans- 

 verse process of the right side of the atlas, toward Avhich the head 

 was bentj formed a new articulation with the under surface of the 

 jugular process of the occipital bone, " a small synovial cavity sur- 

 rcmnded this acquired articulation, but there was no appearance of a 



* Journal of Anatomy and Physiology, 1888, j). 595. 



