LYMPH-FLOW AND LYMPHATICS, CHICK EMBRYOS 431 



new lymphatics in the allantois and the deep pelvic region, which 

 monopolize the function of the lymph heart in chicks of 8 days 

 and over, seems to be responsible for the second reversal of 

 circulation in the superficial lymphatics. 



ESTIMATES OF THE RATE OF LYMPH FLOW AT DIFFERENT STAGES 



In keeping records of the character of the lymph flow at 

 various stages, the rate of circulation was described somewhat 

 vaguely as slow, moderately fast, or fast. I therefore attempted 

 a few experiments in order to arrive at a more definite estimate 

 of the lymph-flow. For this purpose, a few granules were in- 

 jected into a superficial channel and the point of injection marked 

 by a small extravasation. The time in seconds consumed in 

 the passage of a single granule from this point of injection to a 

 certain easily recognizable point such as the axilla, or the entrance 

 to the lymph heart was then recorded. Subsequently the lym- 

 phatics were injected and the lymph channel under consider- 

 ation drawn with the camera lucida. The length of this channel 

 between the two points was measured in the drawing and the 

 degree of magnification calculated. In making such estimates 

 it was necessary to procure a record in the intervals of rest when 

 the circulation was not disturbed or arrested by the muscular 

 movements of the chicks. 



The following estimates were made by this method: 



1) Earliest anterior circulation in a 16 mm. chick. A 

 granule travelled 1.6 mm in 1 minute, 30 seconds. The rate of 

 circulation in this embryo was 1.06 mm per minute. This is 

 the type of circulation which was designated as 'slow' in the 

 records. 



2) As an example of 'moderately fast' circulation, the flow 

 for this same region was estimated in a chick of 19 mm. The 

 granule under observation travelled 3.8 mm in 30 seconds, a 

 rate of 7.6 mm per minute. 



3) For an estimate of the so-called 'fast' circulation a record 

 was made of the lymph-flow in a channel of the pelvic region dur- 

 ing the period following the pulsation of the lymph heart, in an 

 embryo of 20.5 mm. In this case, a granule travelled 2.44 mm in 

 15 seconds, a rate of 9.76 mm per minute. 



