November 5, 1920] 



SCIENCE 



425 



discoveries. We now know that connective 

 tissue cells, among which the corneal cor- 

 puscles and the cells of Descemet's. membrane 

 are classed, are motile; and as cells endowed 

 with movement they are attracted by certain 

 stimuli called "chemical," such for example 

 as arise in tissue constituents acted on by 

 chemicals and in other ways. Moreover, as we 

 now know, these fixed tissue cells readily 

 multiply in vitro, and thus we arrive at the 

 conclusion that the chemically altered spot in 

 the cornea attracts toward itself neighboring 

 uninjured, motile corneal and other cells, that 

 these cells aggregate about the site of the in- 

 jury and even multiply there, and thus give 

 what may be called a spurious appearance of a 

 collection of pus cells. For it should be re- 

 membered that we are dealing with a period 

 in which tissues were not yet being stained 

 with certain nuclear and other dyes that bring 

 into view brilliant and subtle distinctions of 

 cellular structure ; but that the " inflamed " 

 cornea was merely silvered in order that the 

 cell outlines might become perceptible, and, if 

 desired, was subsequently stained with hema- 

 toxylin to show the nuclei. 



This practise of putting to the test new dis- 

 coveries and contentions even under somewhat 

 hostile circumstances was not a poor discipline 

 for the future teacher of pathology in the 

 United States. The experience may indeed 

 be regarded as having brought into play 

 under favoring circumstances a critical fac- 

 ulty inclined perhaps to leniency, while it held 

 up as it were to the mirror of his perceptions 

 in a somewhat summary fashion the facts of 

 the ultimate and ineradicable residue of per- 

 sonal bias in all men, no matter how great. In 

 the long future years during which Welch dis- 

 pensed knowledge and, what is rarer, wisdom 

 at the Johns Hopkins University and else- 

 where, he came as near as it is perhaps pos- 

 sible for a mere mortal to come, in escaping 

 the blemish of preconception and prejudice and 

 in preserving and presenting the ideal of the 

 open though balanced mind. 

 ' But it would be wrong to infer that there 

 was not also a constructive side to this period 

 with von Recklinghausen. The pathologist 



was great in attainments, and stimulating as 

 a teacher. He engaged Welch in discussion 

 of many topics in pathology which were cur- 

 rent at the time. One of these related to the 

 origin of tumors, regarding which von Eeck- 

 linghausen was endeavoring to formulate his 

 views along lines which have since become 

 more familiar. He inclined to the conception 

 that a kind of fertilization, whether by conju- 

 gation or otherwise, took place among the 

 cells, leading to the unconstrained multiplica- 

 tion characteristic of cancer and other tumors, 

 in consequence of which irregularities of di- 

 vision arose that were the striking obvious 

 signs of the cellular abnormality. Welch al- 

 ways retained an admiration for von Reck- 

 linghausen as a great pathological anatomist. 



The first European adventure was now ap- 

 proaching its conclusion and was to receive a 

 suitable ending by a first visit to Paris and a 

 second to London. It is far simpler and more 

 satisfying perhaps to leave to the imagination 

 the picture of Welch in the great and beauti- 

 ful French city with its wealth of present in- 

 terests and of historic backgrounds everywhere 

 insistent. The fact may, however, be men- 

 tioned that time was found during the two or 

 three weeks of his stay to hear Ranvier, whom 

 he admired greatly and whose book on histol- 

 ogy had been his guide, and to visit the main 

 hospitals. In London he heard Lister lecture 

 at King's College Hospital, and shared in the 

 prevailing excitement which arose from Lis- 

 ter's daring surgical exploit of opening the 

 knee joint. The next was the final act, 

 namely, taking ship at Liverpool for the 

 United States. 



The arrival in itSTew York in the spring of 

 1878 brought forward a question which could 

 be permitted to remain in the background in 

 Europe, but now must be answered. Un- 

 doubtedly Welch possessed wares garnered at 

 home and abroad — ^but to what market were 

 they to be taken? That the practise of medi- 

 cine would be a necessary corollary to any 

 other ambition he might indulge, seemed never 

 to have been doubted by him. Where else were 

 the necessary pecuniary rewards to come from ? 

 There seemed no alternative but to decide im- 



