282 Dr. A. B. Macallum. On the Demonstration 



slightest degree impregnated with iron from the instrument. Zaleski,* 

 has also found that, in sections of the liver made in the usual way, 

 there is nothing in the distribution and quantity of iron present, 

 different from what is observed in sections of the same piece of tissue 

 prepared with a glass knife. 



Having ascertained the conditions, generally, under which the pre- 

 sence of iron is successfully demonstrated in chromatin, I tried once 

 more the experiments with those tissues which can readily be obtained 

 free, at least, from haemoglobin. I found that the reaction came out 

 definitely and distinctly with the chromatin of the corneal and 

 cutaneous epithelium, and in the nuclei of the cartilage cells of 

 Necturus. Here, as in the other instances, the time required for the 

 production of the reaction was found to vary greatly, and two pre- 

 parations from the same organ, e.g., the cornea, presented differences 

 in this respect. 



I have succeeded in obtaining the iron reaction in the chromatin of 

 the cells of the following organs and tissues of Necturus : testicle, 

 ovary, gastric and intestinal epithelium, gastric and intestinal glands, 

 pancreas, liver, kidney, cartilage of tongue and shoulder girdle, the 

 cutaneous epithelium, the mesenteric endothelium and connective 

 tissue, and the muscularis of the intestine. I found also fche iron 

 reaction in the chromatin of red, white, and fusiform cells of the 

 blood. 



From two human placentae of about five and seven weeks respec- 

 tively, thoroughly freed from haemoglobin before hardening, and 

 having the appearance of bleached linen, I removed portions, which 

 I washed carefully with a mixture of alcohol and sulphuric acid to 

 deprive them of traces of haematin, and subjected them to the action 

 of warm ammonium sulphide on the slide. The nuclei of all the 

 isolated epithelial cells of such ga.ve a beautiful and intense iron re- 

 action after ten days. Indeed, certain parts of the preparations 

 reminded one of the iodine-green nuclear stain, but after being three 

 weeks in the warm oven, the colour became greenish-black. The 

 nuclei of the haematoblasts in the villi give the iron reaction in twenty- 

 four hours, and about two to four days are required to show that the 

 masses situated in the eosinophilous amoebocytes scattered through 

 the connective tissue of the villi also contain iron. 



The iron reaction was obtained at the end of two weeks in the 

 nuclei of the epidermal cells of a foetal kitten removed at about half 

 term from the recently killed cat in a way to prevent the absorp- 

 tion of, or contamination with, haemoglobin. 



Treatment of sections of the placenta of the cat with warm 

 ammonium sulphide also shows, as I expected, that with the passage 

 of chromatin from the maternal to the foatal tissues, there is also a 

 * Loc. cit., p. 483. 



