234 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



found in the thymus. Certain " luteal " cells, non-granular to all 

 appearance, occur in the stroma of the chicken's ovary, and may be true 

 interstitial cells furnishing an internal secretion. If it be true that the 

 cells hitherto described as " interstitial " are leucocytes, this will explain 

 the irregularities in their distribution in the ovary and the discrepancies 

 in the accounts of various authors as to their occurrence or non-occurrence 

 in the testis. J. A. T. 



Diet and Testicular Degeneration in Rat. — Ezra Allen (Anat. 

 Record, 1919, 16, 93-117, 2 pis.). Eeduction in the quantity of water- 

 soluble vitamine in the diet of rats results in total degeneration of all 

 the germ-cells of the testis, but does not interfere with growth and 

 development in other respects. The Sertoli tissue persists. The inter- 

 stitial tissue is hypertrophied. The type of degeneration of the germ- 

 cells is like that produced by direct X-ray treatment of the testes. The 

 Sertoli tissue is a syncytium. J. A. T. 



b. Histology. 



Protoplasm and Cell Contents. — "VV. M. Bayliss {Report Brit, 

 Ass., 1919, 117-22). Protoplasm in its simplest form is a liquid 

 with particles suspended in it which may show Brownian movement. 

 It is a dispersion of a more solid phase in a more liquid or watery 

 phase. A great variety of structures can be produced l;)y fixing reagents, 

 but it is impossible to say which, if any, of these corresponds to the 

 living state. The vacuole around the ingested alga in an amoeba is 

 spherical ; an organism like Badhamia, filled with the brown spores of 

 a fungus on which it feeds, can be filtered clear through cotton-wool ; 

 a needle can be repeatedly drawn through protoplasm without injuring 

 it in any way. All these facts point to the conclusion that living 

 protoplasm is a liquid. Ultra-microscopic examination of living nerve- 

 cells, the only constituent cells of the tissues of higher animals as yet 

 examined in this way, shows numerous particles in Brownian movement. 

 From the hydrosol state protoplasm may occasionally pass to the state 

 of a gel, when the shimmering movement suddenly ceases. This 

 change is related to functional activity, and may be produced by weak 

 electrical stimulation. Here are possibilities of the formation of 

 membranes, doubtless of a gel nature, within the protoplasm, as is shown 

 by the occurrence of different reactions at the same time in the same 

 cell. It is as if the cell contained many minute factories. " Proto- 

 plasm is an extraordinarily complex heterogeneous system of numerous 

 phases and components, continually changing their relations under the 

 influence of electrolytes and other agents." J. A. T. 



Nature and Permeability of the Cell Membrane. — W. M. 

 Bayliss {Report Brit. Ass., 1919, 122-37). "Although protoplasm is 

 a hydrosol of low viscosity, it does not mix with water, remaining, while 

 alive, as a separate phase. If ' killed,' as by an electrical shock or the 

 application of an anaesthetic, it freely mixes with the surrounding 

 watery solution. In the normal state it must be surrounded by a film 



