118 CARNEGIE INSTITUTION OF WASHINGTON. 



In an article by W. B. Martin on neutral stains as applied to the 

 granules of the pancreatic islet cells, a method is set forth for staining 

 the granules in the cells of the islets of Langerhans by which the A and 

 B cells can be differentiated from each other and from the cells of the 

 parenchyma as well. This method is founded on Bensley's neutral 

 gentian method, but makes use of a number of new neutral stains. 

 The neutral dyes are obtained by combining various acid dyes of the 

 azo series with certain of the basic triphenylmethane dyes. A list of 

 these neutral compounds is given, with a brief description of the prop- 

 erties and the relative merits of each as a granular stain. It is shown 

 that at least two of these dyes — e. g., neutral azofuchsin is obtained by 

 combined hexaethylpararosaniline with azofuchsin, and neutral ethyl- 

 violet resulting from the combination of orange G with the same basic 

 stains — are distinctly superior to neutral gentian as a differential gran- 

 ular stain. This superiority lies in the fact that they are both very 

 intense stains, giving a brilliant color contrast in the section and re- 

 sisting well the action of differentiating agents. 



Some very important observations have been made by M. R. Lewis 

 on the growth of muscle-cells. Tissue cultures were made from pieces 

 of the limb-buds of 4, 5, 6, 7, 8, 9, and 10 day chick embryos explanted 

 in Locke's solution and the abundant growth of skeletal muscle tissue 

 and connective tissue which arose from the explanted piece was kept 

 in a healthy condition — i. e., with numerous mitotic divisions, often as 

 one mitotic figure in every four or five resting cells — by bathing the 

 growth each day with Locke's solution, to which had been added 0.5 

 per cent dextrose and either a trace of yolk or a small quantity of 

 chicken bouillon. 



Occasionally among the numerous muscle fibers of such a growth one 

 may be seen to contract rhythmically for varying periods of time. The 

 time interval of the rhythmical contraction is different for each fiber 

 or myoblast. Some contract rapidly — 120 times a minute; others only 

 once in 200 seconds, and some not oftener than once in from 1 to 5 

 minutes. 



An attempt was made to stimulate the muscle-fiber of the growth to 

 contract rhythmically, as was done by Howell with the terrapin heart, 

 by Loeb with the frog skeletal muscle, Stiles with the smooth muscle of 

 the frog, and Lingle with the ventricle of the terrapin heart. Although 

 the results were not sufficiently definite to permit of any conclusion in 

 regard to which one of the salts stimulates the muscle to contract, 

 nevertheless the observations show that by some thus far unknown 

 change, either in the tissue itself or in the surrounding medium, the 

 myoblast and also the muscle-fibers of the skeletal muscle of the chick 

 embryo may be stimulated to contract rhythmically when entirely 

 free from nerve influence and subject only to the stimuli which emanate 

 from their environment. This property is inherited from cell to cell,. 



