MODERN BIOLOGY 541 



The most important progress is coupled with the names of Alexander Rol- 

 LETT (1834-1903) and Theodor Wilhelm Engelmann (1843-1909), both 

 professors of physiology, the former at Graz and the latter first at Utrecht 

 and afterwards in Berlin. Both of them have done service in ascertaining 

 the regular sequence of the cross-stripes in the muscles. Rollett is responsi- 

 ble for these formations' being denoted, as they still are, by letters. Engel- 

 mann, a disciple of Gegenbaur and a distinguished investigator in many fields 

 of research, made a special study of the physical qualities of muscle — the 

 condition of the various elements in normal and polarized light, upon con- 

 traction and relaxation. These results led to a one-sided physical view of 

 muscular action, which was still further advanced by Helmholtz's and other 

 physiologists' investigations into the mechanics of muscular action. On the 

 other hand, Emil Holmgren (i866-i9ix), professor of histology at Stock- 

 holm, Sweden, held a more morphological conception of the muscular 

 process; by careful experimental and microscopical studies of the granular 

 formations which, thanks mostly to G. Retzius, were already known, which 

 are situated between the cross-sections of the various fibrills, he discovered 

 that the granules are the organs which bring about the change of substance 

 in the muscle during action; his views were accepted and elaborated by 

 AuGusTE Prenant, professor at Paris and well known as an unusually many- 

 sided cytologist and author of that both extensive and intensive work en- 

 titled Traite de cytologie. We can deal only briefly with the various categories 

 of supporting tissue — connective tissue, cartilage, bone. In this field of re- 

 search a number of investigations, important from the point of view of prin- 

 ciple and masterly in their technique, have been carried out by, inter alia, 

 Ranvier, Flemming, Studnicka, and the Dane F. C. C. Hansen; these have 

 discovered especially the origin of the categories of supporting tissues and 

 their transitions into one another.^ 



Discovery of fertilisation 

 Undoubtedly the greatest service to biology that has been performed by 

 modern cell-research, however, is its having given us our present knowledge 

 of the course and significance of fertilization — a discovery worthy to be 

 placed by the side of the explanation of the circulation of the blood in the 

 seventeenth century. If, however, we compare the course of these two great 

 achievements in the field of research, we get a striking impression of the con- 

 trast that exists between scientific activities nowadays and those of a couple 

 of centuries ago. On the one hand, Harvey, who spent twenty years or so 

 quietly and peacefully examining the idea that had been kindled in him in 

 his youth, and who afterwards submits it to the world in its perfect and 



^ Accounts of the development of cell research in more modern times will be found in 

 Prenant's above-mentioned work, in M. Heidenhain's Plasma und Zelk, and in other histological 

 text-books, to which the reader is referred. 



