10 CHARLES R. STOCKARD 



To give a general idea of the way in which the embryos devel- 

 oped in these different grade solutions of alcohol, I may cite some 

 of the details of one experiment. After forty-eight hours many 

 eggs are dead in all the solutions. The dead eggs are thrown 

 out. When seventy-two hours old many others are dead in the 

 solutions with 1.5 cc., 2 cc., 2.3 cc., and 2.6 cc., while all but one 

 individual had died in 2.8 cc. It should be added here that 

 about seventy-five eggs are placed in each dish. From the 1.5 

 cc. solution sixteen are alive at seventy-two hours, several with 

 various eye defects, the hearts are beating but contain colorless 

 fluid and the only trace of red blood color is in the intermediate 

 cell mass and caudal vein. Several others of this lot have a 

 full circulation with corpuscles in the current. From the 2 cc. 

 solution one has a feeble heart beat but no blood is visible and 

 there is no circulation; some embryos have no circulation but 

 blood is present in the posterior end of the body, while many 

 have blood circulating with a strong heart beat. 



This brief reference to the notes of the experiment show that 

 such doses are just on the border line of effectiveness since some 

 individuals in the solutions are not able to develop a circulation, 

 while others with a higher degree of resistence do develop a 

 more or less normal circulation. It is very important in such 

 experiments to use these threshold doses since they are the least 

 injurious possible to give the desired result. In this way one 

 gets individuals which have no circulation of the blood, and, 

 therefore, in which the blood anlage develops and remains in its 

 permanent position, without having any serious defects or ab- 

 normalities in the general body tissues of the embryo. 



From a study of such specimens carefully controlled by a study 

 of normal individuals, one is fully justified, I believe, in drawing 

 final conclusions as to the significance of the developmental 

 processes taking place. It cannot be argued so far as the blood 

 anlage is concerned that the conditions recorded are pathologi- 

 cal or other than those which would occur in a normal genesis 

 of the blood except that it never circulates. 



Embryos which are intended for microscopic study have 

 been prepared in the following manner: The eggs are placed 



