EARLY PULSATIONS OF LYMPH HEARTS 389 



body movements nor lymph heart beats were observed. When 

 the body movements were paralyzed by chloretone, the groups 

 of periodic lymph heart beats ceased and an increased number 

 of single pulsations occurred, at irregular intervals. There were 

 approximately eight beats per minute (charts 1 and 2: Stage 4). 



Stage 5. Finally, in embryos of 10 to 13 days, the lymph 

 heart contractions were found to be quite independent of the 

 periodic body movements. At this stage, there was no semblance 

 of periodicity in the pulsations of the lymph heart. Beats were 

 seen to occur during the periodic spasms, but the intervals between 

 such beats were not shorter than between those occurring in 

 the period of rest. On the other hand, we observed several 

 spasms during which no lymph heart beats whatever occurred 

 (charts 1 and 2: Stage 5). 



After the recovery from chloretone in Stages 2, 3 and 4, al- 

 though the isolated number of heart beats was always greater 

 than those occurring before the anesthesia, the total number of 

 beats per minute remained practically the same. Also the number 

 of beats per minute occurring during the period of anesthesia was 

 not materially changed from the number originally present, in 

 each of these stages (see chart 2). Although the chloretone 

 dissociates the lymph heart pulsations from the body move- 

 ments and greatly alters the rhythm in Stages 2, 3 and 4, it does 

 not change, to any noticeable degree, the total number of 

 l3miph heart beats. Stage 1 is the only stage in which the func- 

 tion of the IjTiiph heart is seriously interfered with, by the addi- 

 tion of chloretone, for in this stage only is it inseparably con- 

 nected with the functioning of the voluntary muscular apparatus. 



SUMMARY 



We find, then, that pulsation of the lymph heart first appears 

 in embryos of six to seven days (19 to 22 mm.) and that, at this 

 earliest stage, the beating of the lymph heart is intimately con- 

 nected with the periodic muscular movements of the embryo. 

 Lymph heart contractions accompany the periodic spasms, never 

 occur in the interim between body movements and each beat 

 is invariably accompanied by a contraction of the tail. When 



