of the Presence of Iron in Chromatin'. 283 



transference of iron to the embryo. At the base of the placental 

 mucosa, there are glands whose cellular elements pass through a 

 history not unlike in some respects that of the mammary gland. 

 They proliferate, enlarge in size, apparently extrude particles like fat 

 into the lumen of the gland, and then they undergo chromatolysis. 

 The masses of chromatin set free can be readily recognised in the 

 debris. In some cases the upper wall of the gland is broken through 

 by the extremity of a villus, whose elongated epithelial cells now 

 stretch amoaba-like towards the debris, particles of which th^y invag- 

 inate, and among these, chromatin granules. The latter finally reach 

 the centre of the villus> and, with the chromatin obtained from dis- 

 integrated maternal endothelial cells, form there a more or less 

 compact column of chromatin. When the embryo measures 25 mm. 

 in length, the amount of chromatin is small, but in considerably 

 later stages it is so abundant that, in stained sections of 30 /* in 

 thickness, the masses formed of it can be seen with the naked eye. 

 In the younger placenta the chromatin gives, with warm ammonium 

 sulphide, the reaction at the end of twenty-four hours, but the pre- 

 sence of iron is not indicated by hydrochloric acid and potassic ferro- 

 cyanide. In the older placentae, the acid and ferrocyanide mixture 

 gives the iron reaction with the chromatin masses at once, as does 

 also the ammonium sulphide. Now, the chromatin granules in the 

 debris of the glands at the base of the placenta do not in any case 

 give a reaction with the acid mixture, while with warm ammonium 

 sulphide they show the presence of iron after two days. From this 

 it is to be concluded that the chromatin of disintegrated cells mani- 

 fests more and more readily as time goes on the reaction with 

 ammonium sulphide, and my experiments with this reagent on de- 

 generating cells in other organs confirm this conclusion. 



Now in such sections of the placentae, the chromatin of none of the 

 ordinary cells gives the reaction, even if the sections are kept for 

 weeks in contact with warm ammonium sulphide, either in a bottle 

 or under a covered glass. If the cells are teased out from one another, 

 so that they lie free and separate under the cover, the reaction is 

 obtained in each in about ten days, and it is as distinct as in the 

 chromatin granules in the glandular debris, or as in the masses in the 

 central parts of the villi. 



I have also obtained the iron reaction in the chromatin in the intes- 

 tinal cells and the maturing ova of Oniscus, in the nuclei of the 

 maturing ova, and of the spermatozoids of Ascaris mystax, and in the 

 smaller cells of the larvas of a species of Ckironomus found on the 

 stones in running water in the neighbourhood of Toronto in winter. 

 The cells of the salivary gland of the latter animal are too large to 

 give the reaction readily, and, as I write, it has only now begun to 

 appear in the nucleolus in which the chromatin filament terminates. 



