429 PROCEEDINGS OF SECTION D. 
experimenting with separated cells from multicellular organisms, 
and especially with unicellular animals and plants. By such means 
we may hope to discover some general laws regulating the activities 
of protoplasm. At the same time, the number of researches upon 
the more lowly animals belonging to the invertebrata is rapidly 
increasing. The physical properties of protoplasm, such as con- 
sistence, specific gravity, optical properties, have been re-examined, 
and the first disintegration productsof the destruction of protoplasm 
are beginning to be studied with renewed vigour with the object of 
ascertaining what special molecular arrangement may be charac- 
teristic of living matter. 
The intimate structure of cells is becoming of equal importance 
to the physiologist as to the morphologist. All the detailed 
changes of structure in cell and nucleus which may be manifested 
during activity, whether it be division of the cell, fertilisation, or 
secretion, are being assiduously studied. Interesting changes in 
the chemical properties of different parts of the cell-nucleus and 
nucleolus, as shown by alteration in their reaction to various 
staining agents have been carefully observed. Some rough idea of 
the difference in chemical composition of different parts of the cell 
has been ascertained, as, for instance, the increased amount of 
phosphorus-containing compounds in nuclei. We know also that 
the chromatin is largely composed of nucleins, whereas the nuclear- 
sap is made up of some other albuminous matter. 
Another series of observations which will likely prove of much 
value are concerned with the response of cells to different kinds 
of stimuli, chemical, mechanical, electrical, light, gravity, &e. The 
study of chemotaxis, the name given to the movements of a cell, 
animal or vegetable, towards or away from the presence of small 
quantities of some chemical body, has already assisted greatly in 
our understanding of inflammation, that protective reaction of an 
animal against the introduction of noxious material from without. 
Chemotaxis also plays a part in the fertilisation of ferns and 
mosses. Slight traces of some body are dissolved out of the female 
organs. This attracts the spermatozoids and directs their move- 
ments towards the position of greatest concentration, viz., the 
neighbourhood of the female cells. Some such directing force may 
operate in bringing the spermatozoa of animals into contact with 
the ova. This may apply alike in those cases where both are dis- 
charged free into the water, and also where the spermatozoa ascend 
the oviducts against ciliary action. The effects of alteration in 
temperature, desiccation, and changed environment generally upon- 
all kinds of organisms are being assiduously studied, and every- 
where increased attention is devoted to the elementary phenomena 
of living things, and just as the physiology of the last half century 
has been essentially an organ-physiology, the new departure must 
be characterised as a cellular-physiology. 
