November 



1891.] 



SCIENCE. 



275 



But the latest expressions on the subject show an evidence 

 of the reiudorsement of the original statements. 



In 1850 (Proc. Phil. Acad. Nat. Sci., 201) Dr. Leidy per- 

 formed some experiments upon the transplantation of can- 

 cer. Talking several fragments of a cancerous tumor from a 

 human subject he inserted them beneath the skin of living 

 frogs. After au interval of five months had elapsed the 

 frogs were killed and the localities in which the sections had 

 been inserted were examined. Tn all but one instance they 

 were found to be living and united to the host by vascular 

 attachments. The characteristic cancer cells, however, had 

 in great part disappeared. Dr. Leidy believed that similar 

 experiments on warm-blooded animals might increase the 

 number of viable cancerous elements. The transplantation 

 of tissue from one animal to another was not novel, but the 

 facts of these experiments proved that cancer might be in- 

 oculable, — a statement which was novel, and has been dis- 

 puted since. The observation was in the line of most impor- 

 tant research, and the recent experiments embracing the 

 successful transfer of the human hypertrophied thyroid body 

 from the neck to the abdomen of the same individual have 

 been essayed with important practical results. They again 

 demonstrate thai Dr. Leidy's mind was not one limited 

 merely to the line of description. At the time of these ex- 

 periments Dr. Leidy was conducting a course of physiologi- 

 cal instructions to medical students. No doubt remains that 

 ■had he chosen physiology as a branch of research that he 

 would have been signally successful. 



In 1852, Dr. Leidy created from the species Hippopotamus 

 liberiensis, Morton, a new genus, Choerodes, which was 

 founded upon the skeleton of a young individual. In the 

 •Journal of the Philadelphia Academy for 1850-54 this form 

 was renamed Chceropsis, since Choerodes was found to be 

 previously assigned to a genus of insects. Abundant mate- 

 rial of the adult has since been received in Paris and made 

 the basis of an elaborate memoir by Alphonse Milne-Ed- 

 wards, who has confirmed Leidy's diagnosis in every partic- 

 ular. 



Opinions have differed widely as to the nature of dental 

 caries. One set of observers claimed that it was due to vital 

 or general conditions affecting the economy; another in- 

 sisted that the disease was due 10 forces acting entirely from 

 without. Since the bacteriological method of research has 

 been introduced into medicine this difference of opinion no 

 longer exists, for all agree that the statement last made is 

 the correct one. Dr. Leidy in 1870 (Proc. Phil. Acad. Nat. 

 Sci., 133) demonstrated in the subject of an old man that a 

 single tooth remaining in the lower jaw was free from caries 

 owing to the fact that it was imbedded in the bone. He thus 

 demonstrated that caries was caused by extraneous condi- 

 tions, for the disease was controlled by vital states of the in- 

 dividual, it was unreasonable to infer that they would not 

 long before have attacked and destroyed the tooth that had 

 so long remained in the jaw. This fertile suggestion antici- 

 pated the discovery of the baciUar origin of dental caries 

 made by one of his pupils. Professor Miller of Berlin, several 

 years afterward. The announcement of a new species of 

 fossil horse and of a new species of Pajbrotherium, in 1847, 

 brought to Dr. Leidy a reputation for acumen in the study 

 of fragments of skeletons, and the study of the treasuies of 

 fossil remains in all sections of our country soon controlled 

 his energies. Wliile this work is strictly anatomical, its re- 

 lations are in the main with geology; it is so vast in quan- 

 tity that no attempt can be made here to discuss it, even if 

 your speaker were competent to do so. This much can be 



said in dwelling upon his qualifications as an anatomist, so 

 far as I know, there is but one instance of his having made 

 an error in statement.' Attempts to protect from error often 

 go with timidity, if they are not due to it. But in Leidy's 

 case it was not over caution that saved him from error, but 

 too correct primal impressions of the objects he studied. His 

 powers of application were amazing, and the correctness of 

 his conclusions was due to swiftly drawn deductions from 

 the existing premises, and not to surmises or to feats of the 

 imagination. In illustration of his ability may be men- 

 tioned his discovery of Uineatherium, — this genus he es- 

 tablished upon a few fragments. Entire skeletons were after- 

 ward discovered, and two observers, independent of one 

 another, endeavored to found distinct genera upon them. 

 But all later writers have claimed that Uineatherium was 

 indubitably founded on the fragments described by Leidy. 



Exceptional ability in drawing just inferences from im- 

 perfect material signalized Leidy's labors in other directions. 

 He delighted in this kind of work, and numbers of short 

 communications were made by him on abnormalities. 

 Among these may be mentioned the note on the dissection 

 of a male hog, showing arrest of development in the organ 

 of generation (Proc. Phil. Acad. Nat. Sci., 1870, 65); on 

 " polydoctylism " in the horse (Proc. Phil. Acad. Nat. Sci., 

 1871, 112) and an account of a buffalo 9sh with congenital 

 narrowing of the mouth (Proc. Phil. Acad. Nat. Sci., 1875, 

 125). 



He was the tirst authority in the country on questions of 

 disputed identifications. On one occasion a number of al- 

 leged fossil bones were sent him for examination, which 

 proved to be inorganic concretions. On another a specimen 

 which a zealous physician thought to be a new genus of 

 parasite from the human intestine proved to be the fragment 

 of imperfectly digested orange pulp. On yet another, a 

 number of bones were sent to him by a physician who ob- 

 tained them from a woman who claimed to have been preg- 

 nant. They were shown to be the bones of an embryo hog. 



Dr. Leidy's communications on human anatomy have not 

 been numerous, but they all exhibit the same closeness of 

 observation, and cautious yet far-reaching conclusions. 



In 1849, Dr. Leidy redescribed and placed on better foun- 

 dation the thyreo epigloltideum muscle. In 18— he studied 

 the development of the human temporal bone and described 

 for the first time the attic or upper chamber of the middle 

 ear. The term "attic" has come into general use with 

 aurists. He also entered into a critical revision of the com- 

 ponent parts of the petrosa, and corrected several errors into 

 which no less authority than Huxley had fallen. His well- 

 known work on human anatomy appeared in 1860. It 

 was prepared especially for the use of his students at the 

 university. The most noteworthy feature in this work was 

 an attempt to anglicize anatomical nomenclature. In the 

 second edition, which appeared in 1889, the same intent to 

 reform nomenclature is apparent. This department of peda- 

 gogy, while of English origin, has had its most earnest ex- 

 ponents in America, and Dr. Leidy's labors in the field will 

 hold always an honorable position. In his teaching, Dr. 

 Leidy held to the existence of a vocal membrane in the lar- 

 ynx, rather than a vocal cord. His demonstration of the 

 temporal muscle was original and clearlj- demonstrated the 

 existence of two layers arising in an unditfereniiattd mass 

 at the posterior part of the lempoi-al fossa. 



» He identified a fragment of the mandible of Bathysrathus as belonging to 

 the masiila. Oweu invited his attention to it. Leidy said of this, " It was an 

 egregious blunder, I cannot understand how I could have made it." A frank 

 confession of a venial error. 



