io4 The Science of Life. 



Probably all living histologists would agree that the 

 veteran of their craft, of whom they are proudest, is 

 Professor Albrecht von Kolliker. The magnitude of his 

 work, alike in quantity and quality, is a lasting example 

 to the spirit of research. He helped in establishing the 

 cell-theory, he traced the origin of tissues from the 

 segmenting ovum through the developing embryo, he 

 demonstrated the continuity between nerve-fibres and 

 nerve-cells of vertebrates (1845), he isolated the elements 

 of smooth muscle (1848), he did lasting work in connec- 

 tion with the development of the skull and the backbone 

 (1849-1850), and much more, all in the early years of 

 his scientific activity. Since 1850 hardly a year has 

 passed without some important histological, embryo- 

 logical, or anatomical work from Von Kolliker, as may 

 be readily verified by turning up the famous Zeitschmft 

 fur wissenschaftliche Zoologie, which was founded by 

 him and Von Siebold in 1848. 



On the physiological side it was necessary to show 

 in greater detail that the life of the body was to some 

 extent expressible in terms of the internal changes in 

 the constituent cells. Epoch-making in this connection 

 was the work of Goodsir (1845), and Virchow (1858), 

 who demonstrated that both in normal and pathological 

 processes cells arise from pre-existing cells, and that 

 the life of the whole may be spelt out in the life of the 

 parts. 



While most naturalists believe strongly in the struc- 

 Criticism tural, functional, and developmental im- 

 of the Ceil- portance of cells, there have been frequent 

 protests against regarding the cellular stand- 

 point as ultimate. 



(a) Morphological Criticism. That development pro- 

 ceeds by cell-formation is a cardinal part of the cell- 

 doctrine. But it has been pointed out, by Sedgwick 

 (1894) in particular, that in some cases, e.g. the develop- 

 ment of a species of Peripatus, the nuclei divide without 

 corresponding cell-divisions, and the result is a " syncy- 

 tium " or protoplasmic mass with many nuclei, but with 

 undefined cell-boundaries. 



(b) Physiological Criticism. That the organism lives 



