20 TBANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



animal food, proteid, albuminoid, fat, sugar and salts, and 

 they are elaborated in these cells. Such elaboration 

 should have at the back of it, definite structural changes 

 in the cells. It seems clear from recent research that, 

 when the secretion is being formed in the gland, the 

 mammary cells alter not only by duplication of their 

 nuclei but by the appearance of specialised chromatin 

 filaments in the cell-substance. Simultaneously with 

 these, fat globules appear in juxtaposition with the new 

 nuclei and with these filaments, and finally the new 

 nuclei, the filaments and the fat are all discharged from 

 the cells into the duct. Here the nuclei and filamentous 

 particles appear to pass into solution, the fat remaining 

 as a fine emulsion.* 



Sixth class of instances ; structural changes associated 

 ivith nervous activity. 



In nervous tissues, by following the same inference from 

 function to structure, definite alterations have now been 

 demonstrated. Let me confine myself to one class of 

 nervous tissues, that associated with vision. 



The nerve-fibres from the retina of the eye start from 

 cells there and stretch back towards the brain, where they 

 end in the immediate neighbourhood of other cells, from 

 which other nerve processes spring. Through all these 

 the mysterious change which we call a nervous impulse is 

 conducted, this in the case of the eye being aroused by the 

 action of light. 



Physiological experiments have shown that such nerve 

 impulses pass through or into special masses of cerebral 

 nerve-cells, localised at the base of the brain in the corpora 

 quadrigemina, etc., and on the surface m the occipital 



* See Steinhaus Die Morphologie der Milchabsonderung, Du Bois Archiv 

 f. Physiol., 1892, Supplement, p. 54. 



