QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 185 
3. Formation of Fibrin from the Red Blood- Corpuscles.—In 
a second part of the same paper, Landois describes the 
formation of fibrin as being dependent on the dissolved 
corpuscles. If a drop of defibrinated rabbit-blood be brought 
into a drop of frog’s serum, the cells aggregate together, and 
become sticky on their surfaces. The cells soon become 
globular, and those cells lying towards the periphery allow 
the blood-colouring matter to pass out. This discolouring 
gradually extends towards the centre of the drop, and at 
last only a heap of stroma remains. The stroma-substance 
is very tough and viscid. At first the contours of the cells 
can be detected ; and, when the stroma has been agitated 
to and fro, the cellular contours disappear, and viscous fibres 
and stripes are observed. Step by step the formation of 
fibrous masses from the dissolved mammalian cells can be 
observed. The author thinks this fibrin should be called 
“stroma-fibrin”’ in opposition to the ordinary fibrin or 
plasma-fibrin, which is formed without solution of the blood- 
corpuscles. The two kinds of fibrin may possibly be chemi- 
cally distinguished from each other. In transfusion, if dis- 
solution of the cells occur, then, of course, the formation 
of stroma-fibrin may take place. The coagulation occurs 
the sooner, the more serous the blood. Animals in a state 
of asphyxia, into whom heterogeneous blood was introduced, 
showed the most extensive coagulation. 
IV. Epithelium.—1l. Cement-Substance of Epithelium.— 
R. Thoma (‘ Centralblatt,’ No. 2, 1875), in studying the physi- 
ological and pathological changes in the epithelium of the frog’s 
tongue, discovered a method by which in the living animal 
an excretion of indigo in the cement-substance of the above 
organ, as well as in certain parts of the alveolar mucous 
membranes, could be produced. This cement-substance 
appears as a fine deep-blue coloured network, stretching 
regularly over the whole tongue, between the colourless 
epithelial cells, and lying somewhat below the level of the 
free epithelial surface. 
The method is the following. A solution of pure sulphni- 
digotate of soda is prepared by diluting, with an equal 
volume of distilled water, a saturated and filtered watery 
solution of indigo. This is injected, under a constant pres- 
sure, into the median abdominal vein of a frog, so that in the 
course of two to four hours from four to six cubic milli- 
métres of the indigo solution are introduced into the body of 
a medium-sized Rana temporaria or esculenta. Simul- 
taneously the tongue is irrigated by a 1°5 per cent. solution 
of chloride of sodium, in consequence of which pronounced 
