86 HOWELL. [Vol. IV. 



consisting of a mixture of borax carmine and indigo carmine. 

 This stain was subsequently abandoned, as it was found not 

 to work as a differential stain for haemoglobin after mercuric 

 chloride hardening. In several cases where sections were 

 made of a foetal femur, with its contained marrow, the tissue 

 was fixed in Flemming's solution, and afterwards decalcified 

 in saturated picric acid solution. These sections treated with 

 the indigo-carmine solution gave very beautifully the apple 

 green stain to the haemoglobin in the red corpuscles. Another 

 method which I used frequently, both for the blood itself and 

 the blood-forming tissues, is one recommended by Flemming, as 

 follows : the fresh tissue is quickly teased upon a slide in its 

 own liquid, and a large drop of diluted Flemming solution is 

 dropped upon it, and the specimen then kept for twenty-four 

 hours in the moist chamber. By that time a number of the 

 cells have become firmly adherent to the slide, so that it can 

 be washed in water. It is then covered with saffranin for 

 twenty-four hours, being kept in the moist chamber. The 

 saffranin is washed off with absolute alcohol, with or without 

 acid, according to the depth of the stain, and the specimen 

 treated successively with oil of cloves, xylol, and balsam. 

 This method gave excellent results. 



Development of the Red Corpuscles during Extra-uterine Life. 



The importance and even the existence of the nucleated red 

 corpuscles has been denied by some authors, as I have at- 

 tempted to show in the historical review of the subject. But 

 that these cells are found in the red marrow of the bones 

 throughout healthy life, and that they give rise to the red cor- 

 puscles of the circulating blood, has been proved beyond any 

 reasonable doubt, and upon the whole is as well accepted as 

 most of the facts of physiology. What we desire, then, is a 

 complete knowledge of the life-history of the nucleated red 

 corpuscle, its origin, its method of growth or reproduction, and 

 the way in which it is changed to the non-nucleated corpuscle. 

 These corpuscles are found chiefly, if not exclusively, in the 

 adult in the red marrow. Hence most of the work has been 

 done upon that tissue. 



