570 REPORT — 1882. 



of tlie pancreas, exhibit differences in size, differences iu tlie form and appearance 

 of tlie nucleus, and differences in the cell contents, coiTesponding to varied states of 

 functional activity. 



Time will not permit my mentioning iu detail the results of these observations 

 from which, however, certain general conclusions appear derivable. Thus, a gland- 

 cell at rest is usually larger than a similar cell which has been engaged iu the pro- 

 cess of secretion ; from its behaviour to reagents, it usually appears to contain 

 within itself aa abundant store of the body or bodies which are chiefly characteristic 

 of the secretion, or closely related antecedents of these, and the amount of undif- 

 ferentiated protoplasm surrounding the nucleus appears to be at a minimum. On 

 the other hand, the gland-cells, which have been secreting for a greater or less period, 

 often, though not invariably, present a diminution in their size, a diminution in 

 the amount of the characteristic bodies previously referred to, and an increase in 

 the protoplasmic constituents of the cell. All facts, histological as well as physio- 

 logical, seem to point to the following conclusion : that during rest, the cell forms, at 

 the expense of, or as the product of the differentiation of, the cell protoplasm, the 

 bodies characteristic of the secretion ; that whilst secretion is going on these leave 

 the gland-cell ; and that, at the same time, the protoplasmic constituents of the latter 

 increase at the expense of the lymph, to be converted secondarily, either at a later 

 period in that particular act of secretion, or in the succeeding period of inactivity, 

 into specific constituents. The researches of Ileidenhain have been conducted upon 

 the glands after these had undergone processes of hardening and staining, the appear- 

 ances observed indicating changes which, though not identical with, at least corre- 

 sponded to various conditions of the gland. Kiihne and Lea and Langley have, 

 however, studied glands in a living condition, and though the appearances were not 

 identical with those observed by Ileidenhain, they entirely confirm these. 



I have not time to do more than refer to the fact that in some at least, though 

 probably in all of the cells of glands which produce secretions containing ferments, 

 there are formed at first bodies to which the generic term of ' zymo<iens' may be 

 applied, i.e. fermenf-f/enerators, from which a ferment is afterwards set free. 



In coiuiection with this part of my subject I may refer to the view, which was at 

 one time held by some, that iu secreting glands the gland-cell ihaving produced the 

 matter of the secretion was thrown off', discharging its contents into the secretion. 

 This process, when it does occur, must be looked upon as exceptional, and as it were 

 accidental. 



Amongst the most striking examples of the success with which physiological 

 experiment and subsequent histological research have been pursued in combination 

 so as to throw light upon the functions of particular cells, I may refer first to the 

 observations of Ileidenhain, secondly to those of Nussbaum on the excretion of 

 colouring matters, artificially introduced into the blood, by the secreting epithelium 

 cells of the renal tubules. I have previously refei-red to the theory of Bowman, 

 according to which the watery and saline constituents of the renal secretion were 

 supposed to be separated by the so-called ' fflomeruli,' whilst the organic solids 

 of the secretion were supposed to be separated by the epithelium ILuing the convo- 

 luted tubes. 



To this theory was opposed that of Ludwig, according to which the whole of 

 the constituents, watery, saline, and organic, were supposed to be poured out of 

 the vessels of the glomerulus, the amount of water however being far in excess of 

 that contained in the liquids when it reaches the pelvis of the kidney. Ludwig 

 supposed that as the secretion passed over the surface of the epithelium lining the 

 complex tubules, processes of ditt'usion occurred between it, on the one hand, and 

 the lymph bathing the tissues lying outside of the basement membrane of the 

 tubules on the other, the direction of the current of water being from without 

 inwards. The anatomical evidence adduced by Bowman was of itself well-nigh 

 sufficient to prove the accuracy of his views, which have however been placed be- 

 yond all dispute by the following observations : Ileidenhain introduced into the 

 blood a solution of sulphindigotate of sodium, usually some time after having 

 divided the spinal cord in the cervical region. On killing the animal some time 

 afterwards and subjecting the kidney to careful examination, it was found that the 



