SCIENTIFIC THOUGHT. 



22. 



Cellular 

 theory of 

 Schleiden 



said to be a German science as chemistry has been 

 named a French science. I have already referred to the 

 great Haller in the last century, who may be called the 

 father of physiology ; to Blumenbach, the comparative 

 anatomist ; and to Liebig and Wohler, who first among 

 chemists succeeded in producing an organic compound by 

 the processes of inorganic chemistry. I have now to add 

 two names, which together mark a great revolution in our 

 ideas of the structure of organisms, and link together 

 the two sciences which had treated separately of the 

 animal and vegetable worlds. About the year 1838 

 Mathias Schleiden l propounded his cellular theory con- 



Treviranus (1776-1837), a learned 

 physician of Bremen, who began to 

 write his ' Biologic oder Philosophic 

 der lebenden Natur' in 1796 and 

 to publish it in 1802 (6 vols., 1802- 

 22). Lamarck used the word in 

 his ' Hydrogeologie,' 1801. They, 

 as well as Bichat about the same 

 time, independently " conceived the 

 notion of uniting the sciences which 

 deal with living matter into one 

 whole, and of dealing with them 

 as one discipline " (Huxley, on the 

 study of Biology, 1876, in ' Ameri- 

 can Addresses,' p. 136, &c.) The 

 term, though of German origin, has 

 not found favour in that country, 

 and after having been used officially 

 in France and England, makes its 

 appearance in Germany only since 

 the great works of the modern 

 English school, headed by Darwin, 

 have gained so much influence in 

 Germany. In the meantime the 

 biological sciences had been exten- 

 sively represented at the German 

 universities by chairs of physiology, 

 zoology, botany, &c. According to 

 Huxley, biology has been " substi- 

 tuted for the old confusing name 

 of natural history," and "denotes 

 the whole of the sciences which 



deal with living things, whether 

 they be animals or whether they 

 be plants" (loc. cit., p. 138). It 

 can be divided into three branches 

 (1) Morphology, which comprises 

 the sciences of anatomy, develop- 

 ment, and classification ; (2) the 

 science of the distribution of living 

 beings, present and past ; and (3) 

 physiology, which deals with the 

 functions and actions of living 

 beings, and tries to "deduce the 

 facts of morphology and of distribu- 

 tion from the laws of the molecular 

 forces of matter" (Huxley, 'Lay 

 Sermons,' &c., p. 83, 1864). To 

 these three Huxley adds (' Ency. 

 Brit.,' art. "Biology") the infant 

 science of "aetiology," which "has 

 for its object the ascertainment of 

 the causes of the facts of biology 

 and the explanation of biological 

 phenomena, by showing that they 

 constitute particular cases of general 

 physical laws" (p. 688). 



1 Mathias Jacob Schleiden (1804- 

 81), for some time Professor of 

 Botany at Jena, was a man of 

 peculiar ability and disposition, 

 combining a philosophical mind 

 with exact knowledge and a gen- 

 eral literary taste, not frequently 



