On Cajal's Formalin- Silver Nitrate Impregnation Metliod. 327 



the Cajal method with those furnished by the Golgi (7), Kopsch {Ui), 

 and other techniques is of interest. 



It is now well known that the male gerhi-cells of Molluscs 

 contain a structure called the " nebenkern " or sphere. Recently 

 Gatenby (-5) has shown that this is the representative in the germ- 

 cells of the nerve-cell Golgi apparatus. 



Now, if the spermatogonia or spermatocytes of the Pulmonate 

 or Prosobranch Gastropods, e.g.' Paludina vivipara, be examined 

 intra-vitam and with intra-vicam stains, the Golgi apparatus is 

 seen to be made up of a number of perfectly discrete rodlets, the 

 dictyosomes lying upon and around the archoplasm. Similar 

 material fixed in chrome osmium and stained with Heidenhain's 

 iron-hsematoxylin shows these elements discrete and apparently 

 unaltered in all respects. 



Now the Kopsch, Golgi and Cajal impregnation methods for 

 Golgi apparatus show the Molluscan sperniatogonial and sperma- 

 tocyte Golgi apparatus as a more or less distinct and continuous 

 reticulum. There can be little doubt that this appearance is 

 incorrect, since in the living cells the rodlets are seen to be 

 perfectly discrete. 



The reticular appearance is either caused by the deposition of 

 metallic compounds, particularly around the ends of the Golgi 

 rods, or possibly, by shrinkage, causing the closely-disposed 

 dictyosomes to appear as a reticulum. 



It follows from the above that the Cajal, Golgi and Kopsch 

 impregnation methods, though yielding valuable results, need 

 careful interpretation and control, so far as possible, by other 

 techniques. 



In conclusion, I must thank Professor C. S. Sherrington for his 

 interest in. this work, and my friend Mr. J. Bronte Gatenby for 

 advice and criticism. 



6. Bibliography. 



1. Cajal, E. y. — Algunas variaciones fisiologicas y patologicas del 



aparato reticolar de Golgi, Trab, del Lab, Invest, Biol., Madrid, 

 xii. (Feb., 1915), 



2. Formula de fijacion para la demonstracion facil del aparato 



reticolar de Golgi, etc, Trab, del Lab, Invest. Biol., Madrid, x, 

 (1912), 



3. Trab. del Lab. Invest. Biol., viii. (1910). 



4. Gatenby, J. Bronte. — Identification of Intracellular Structures. Journ. 



Eoy, Micr, Soc, June, 1919. 



5. Cytoplasmic Inclusions of the Germ-cells, Part IV, Notes on 



Dimorphic Spermatozoa of Paludina, etc. Quart. Journ. Micr, Sci., 

 Ixiii, pt, 4 (April, 1919). 



6. Golgi, C— Arch. Ital. de Biol., vii. (1886). 



7. Arch, Ital. de Biol., xlix (1908). 



8. Lee, B. — Microtomist's Vade Mecum, 7thed, 



