EARLY PULSATIONS OF LYMPH HEARTS 375 



At a much earlier stage — in chicks of four and one-half to 

 five days — lymphatic vessels are present, although their size is 

 much smaller, and in embryos of five to six days, the lymphatic 

 plexus, which precedes the definite pulsating lymph heart, nor- 

 mally contains stagnant blood, which enters it through its con- 

 nections with the intersegmental veins of the tail. Preliminary 

 reports of studies made of this lymphatic plexus in living embryos 

 and by the method of injection, have been published. A more 

 complete account of these researches, together with careful 

 microscopic studies of the endothelium is soon to be published. 



In the course of this study of the developing lymph heart, 

 we noticed, while examining a chick of seven days under the 

 binocular microscope, that there occurred several beats of the 

 lymph heart simultaneously with vigorous movements of the tail. 

 As muscular contractions of body, tail and limbs had previous- 

 ly been seen in embryos of various ages, there was suggested a 

 study of the early pulsation of the lymph heart in relation to 

 these movements. 



For these studies we used a binocular microscope, enclosed 

 in a warm chamber which was heated by an electric light bulb 

 or a small alcohol lamp. An opening was made in the shell and 

 the shell membrane over the region of the embryo, was carefully 

 removed. Throughout the observation, the embryo was kept 

 moist by the occasional addition of a few drops of Ringer's 

 solution, warmed to 38 to 39°C. When the eggs were opened 

 in this way, the chicks remained alive and healthy for from five 

 to eight hours. 



THE :muscular moveaients of chick embryos 



When an egg, incubated four days or more, is opened in this 

 manner the embryo is seen to be undergoing violent movements. 

 These mo^^ements are found to belong to two types : one in which 

 the embryo as a whole is moved, with a continuous back and 

 forth swaying motion around the umbilical cord as a center, 

 and the other type, in which the movements are spasmodic and 

 affect various parts of the embryo. The first type is caused by 

 the peristaltic contractions of the amnion, described by von Baer 

 in 1828. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 17, NO. 3 



