RECENT ADVANCES IN SCIENCE. 561 



from them organs arose. The second of his three famous papers — that 

 on the relationship between man and the animals next beneath him — 

 limned in exemplary fashion the parallelism in the earliest development 

 of all animal beings. But beyond this it stepped boldly across the 

 border line which tradition and dogma had drawn between man and 

 beast. Huxley had no hesitation in filling the gaps which Darwin had 

 left in his argument, and in explaining that " in respect of substance 

 and structure man and the lower animals are one. ' ' Whatever opinion 

 one may hold as to the origin of mankind, the conviction as to the fun- 

 damental correspondence of human organization with that of animals is 

 at present universally accepted. 



Omnis Cellula e Cellula. 

 The greatest difficulty in the advance of biology has been the natural 

 tendency of its disciples to set the search after the unity of life in the 

 forefront of their inquiries. Hence arose the doctrine of vital force, 

 an assumption now discarded, but still revealing its influence from time 

 to time in isolated errors. No satisfactory progress could be made till 

 the idea of highly organized living things as units had been set aside; 

 till it was recognized that they were in reality organisms, each con- 

 stituent part of which had its special life. Ultimate analysis of higher 

 animals and plants brings us alike to the cell, and it is these single 

 parts, the cells, which are to be regarded as the factors of existence. 

 The discovery of the development of complete beings from the ova of 

 animals and the germ-cells of plants has bridged the gap between iso- 

 lated living cells and complete organisms, and has enabled the study 

 of the former to be employed in elucidating the life of the latter. In a 

 medical school where the teaching is almost exclusively concerned with 

 human beings this sentence should be writ large: " The organism is 

 not an individual, but a social mechanism." Two corollaries must 

 also be stated — (1) that every living organism, like every organ and 

 tissue, contains cells; (2) that the cells are composed of organic chemi- 

 cal substances, which are not themselves alive. The progress of truth 

 in these matters was much retarded by that portion of Schwann's cell 

 theory, which sought to establish the existence of free cell formation, 

 which really implied the revival of the old doctrine of spontaneous 

 generation. This belief was gradually driven out of the domain of zool- 

 ogy, but in connection with the formation of plastic exudates found 

 a sanctuary in that of pathology. I myself was taught the discontinu- 

 ity of pathological growths — a view which would logically lead back to 

 the origin of living from nonliving matter. But enlightenment in this 

 matter came to me. At the end of my academical career I was acting 

 as clinical assistant in the eye department of the Berlin Hospital, and 



VOL. LXI. — 36. 



