198 SUMMARY OF CURRENT RESEARCHES RELATING TO 



mobile, somewhat fluid, watery albuminoid substance. The inclosure of 

 fibrils is possible, but not probable. (15) In contact with coagulating 

 fluids, the axial cylinder shrinks up into very diverse forms. (16) Be- 

 tween the shrunken axis cylinder and the medullary sheath, or between 

 the former and Schwann's sheath, a space is left. This contains 

 coagulated material in small quantity, is the enlargement of a normal 

 minimal space, probably containing a lymph-like nutritive fluid. (17) 

 Osmium and other reagents produce a "coagulation-sheath" (Gerinnsel- 

 scheide) on the surface of the axis. On this lie the silver precipitate 

 and Frommann's lines. (18) Beyond the " cortex " there are no genuino 

 sheaths — only artificial pseudo-sheaths. (19) Schiefferdecker here differs 

 from Eanvier and from Boveri. (20) Weigert's hematoxylin blood- 

 alkaline method stains the medullary fibres differently according to the 

 chromic salt used in hardening. No special substance appears to be 

 stained, the colouring varies considerably. After hardening in chromic 

 acid, the medulla is little or not at all stained, but the cortex of the axis 

 cylinder is, though not quite regularly. The irregularity in both 

 methods depends apparently on the varying influence of the differentiating 

 fluid. 



Structure of Red Blood-corpuscles.*— Sig. F. Foa, has made a minute 

 study of the structure of red blood-corpuscles. These were stained after 

 Ehrlich's method with methyl-blue, and decolourized by chromic acid 

 • 20 per cent. His results go to show that the red corpuscle is consti- 

 tuted as follows : — (1) A very delicate amorphous membrane ; (2) a 

 layer of haemoglobin ; (3) a reticulum of granular strands converging 

 towards a central corpuscle which represents the residue of the nucleus; 

 (4) the homogeneous protoplasm, probably in two physically different 

 layers. 



Haemoglobin Crystals of Rodents' Blood. f — Prof. W. D. Halliburton 

 has endeavoured to ascertain whether the six-sided crystals of the haemo- 

 globin from the blood of certain rodents really belong to the hexagonal 

 system of crystallographers, and he finds that the presumption in favour 

 of the haemoglobin crystals of the squirrel and hamster being true 

 hexagons is exceedingly great ; those of the mouse do not, however, 

 appear to be so. Another question which naturally arises is as to the 

 difference of crystalline form that haemoglobin presents in different 

 animals, while its other chief properties are universally the same. 

 It is clear that we have either to do with a case of polymorphism, or 

 the crystalline forms are due to the combination of varying proportions 

 of water of crystallization. As to the former suggestion, it is to be 

 remembered that we have not yet a rational formula for haemoglobin, 

 while the conditions which are known to produce dimorphism in minerals 

 — differences of temperature and of solvent — have no influence in the 

 case of haemoglobin. What is stated in the text-books as to the per- 

 centage of water of crystallization, would support the view that there is 

 considerable difference as to its quantity ; but Prof. Halliburton thinks 

 that the variations may be due to the great difficulty in obtaining haemo- 

 globin in a pure state, and to the mode of investigation. Even if the 

 difference in crystalline form is dependent on variation in the amount 

 of the water of crystallization, no explanation is given as to the nature 



* Arch. Ital. Biol., ix. (1887) pp. 28-9. 



t Quart. Journ. Micr. Sci., xxviii. (1887) pp. 181-99. 



