906 
Proceedings of the Eoyal Society 
Generate , may be grouped not only the labours of his immediate 
school, but researches on embryonic layers and tissue structure, 
which form so large a proportion of recent literature. 
(d) Histology had not, however, found in the study of tissues its 
ultimate basis. Yet a deeper mine of morphological inquiry was 
opened up when Schwann referred all plant and animal structure to 
its cellular type and origin. The tissue was analysed to a cell 
aggregate, and that study of cells in their form and structure, in 
their development and modifications, which still mainly occupies 
histologists, was thus fairly initiated. 
( e ) Finally, the researches of Dujardin, von Mohl, Schultze, and 
others directed attention from the cell as such to its all important 
component protoplasm. With this began a new epoch, in which a 
fundamental basis for the study of organic structure is sought in 
the investigation of protoplasm. 
The history of morphology is thus that of a progressive analysis; 
the study of form, so well expressed in the labours of Linnseus, is 
succeeded by the study of organs in the comparative anatomy of 
Cuvier ; while the histological movement inaugurated by Bichat’s 
analysis of organs into tissues is developed in the study of cells 
which Schwann suggested, and finally in the investigation of pro- 
toplasm, which affords the latest and deepest problem of morpho- 
logical research. No deeper analysis is possible, without passing 
out of morphology altogether into chemistry and physics, and we 
are thus warranted in regarding our analysis as practically ulti- 
mate. Along these five great lines of inquiry our morphological 
researches are still progressing towards exhaustiveness, and while 
all, or at least most, of these are combined in any exhaustive mono- 
graph, such as those of the Naples Station or of the “ Challenger ” 
expedition, it is yet in no way arbitrary to classify the labours of 
morphologists as being respectively continuations of the Systema 
Naturae , the Regne Animate , the Anatomie Generate , the Celt 
Theory of Schwann, and Dujardin’s description of protoplasm, or of 
one or more of these. 
§ 3. Physiotogy. — (a) The early physiology, which had not shaken 
itself free from mystical interpretations of the processes of the body, 
but still clung to the hypotheses of animal and vital spirits and the 
like, was little more than a superficial study of habit and tempera- 
