and Laboratory Methods. 1463 



scopically, in a few hours, with certainty from which rabbit the piece of marrow 

 was taken. Moreover, the marrow of the non-iron fed animal lost much of its 

 reddish color, passing into a dirty red, yet never acquiring the looks of the sul- 

 phide of iron preparation. The spleen always, after a term of feeding with iron, 

 was the quickest to color, becoming dark green in a few minutes. This was 

 sometimes true in animals which had received no iron, but the difference in the 

 intensity of the reaction was a ready means of distinction between the animals 

 with and without iron. The mesenteric glands also showed the same difference, 

 taking in iron-fed animals a clear green tone, which became much lessened, or 

 entirely absent, in iron free cases. The pieces of tissue were hardened 24 hours 

 in absolute alcohol, embedded in paraffin, sectioned in different regions, and 

 fastened with albumenized glycerin on the slides ; paraffin dissolved out with 

 xylol, and the sections placed for an hour or so in ammonium sulphide, washed 

 rapidly in distilled water, and mounted in glycerin. In every iron-fed case, in 

 the bone marrow the iron is readily distinguished, especially in thin sections. 

 The iron laden transporting cells, diffusely green, have two to five black green 

 granules. Usually these cells are most abundant in the red marrow, at the ends 

 of the bone, apparently less abundant in the yellow fatty marrow, though abso- 

 lutely more. To study the exact position of these iron cells, the author made 

 preparations after Stieda's method, that is, Berlin blue with alum carmin. The 

 bone marrow of the animals not fed with iron was practically iron free. The 

 spleen of the ordinary plant fed rabbit contained a fair amount of iron, contained 

 exclusively in the pulp. The amount after feeding with iron rose to such a 

 degree that the sections became stained deep green in a second, only the follicles 

 appearing as light, unstained spots. In the mesenteric lymph glands, on ordinary 

 food, solitary green leucocytes can be found ; after an iron diet their number 

 increases in a marked degree. The liver in young animals gives no iron reaction 

 without feeding the substance, but in older animals a small amount is usually 

 indicated. On feeding iron these assume, more slowly and to a less degree than 

 the spleen, the characteristic color showing the presence of iron. This is espec- 

 ially true in the portal regions. The kidneys, only here and there, even with 

 large doses of iron, show single green epithelial cells in the convoluted portions. 

 On the contrary, pieces of the small intestine and colon washed in and left in 

 ammonium sulphide for a short time become green to deep blackish green. The 

 large intestine always gives the strongest reaction. 



The enumeration of the red corpuscles and determination of the hemaglobin 

 were also made. Cover-glass preparations were stained with Ehrlich's hsematoxy- 

 lin and eosin solution. Sections of bone marrow were hardened in alcohol of 

 irkcreasing strength, embedded in paraffin, and stained with eosin-haematoxylin 

 and alum carmin. The spleen and mesenteric glands were similarly treated. 

 For investigation of the special kinds of cells in the bone marrow, Neumann's 

 process was discarded. It was to crush a piece of bone and receive the exuded 

 marrow pulp into a capillary tube, and bringing very small drops from this on 

 to the cover-glass. The author did not employ this method because it seemed 

 to him that marrow cells, as well as the contents of the larger and smaller blood 

 vessels, were obtained. The author arrived at the quantitative relation of the 



