Febkuabt 11, 1916] 



SCIENCE 



209 



needle, or through a slit made with a scissors. 

 Under favorable conditions, the point may be 

 fitted into one of the ostia. The India ink is 

 now slowly injected, and the progress of the ink 

 watched through the transparent vessel walls. 

 In this way, a student can realize what is 

 meant by blood pressure, peripheral resistance 

 of capillaries, physiological pathways open at 

 the time of death, delicacy of capillary beds, 

 as well as the course of the main blood vessels. 

 There is an added advantage, in that one is 

 able to " feel " the resistance of the vessels 

 and capillaries, as well as to see the fluid as it 

 passes through. The addition of a mercury 

 manometer between the bulb and the glass 

 tube may be of use in making quantitative or 

 comparative studies. The advancing stream 

 of black is carefully watched and the order in 

 which the vessels are filled is noted. A very 

 good idea of the relative strengths of the ves- 

 sels is obtained by watching for extravasations. 

 After these points have been observed, the in- 

 jection still remains and can be studied, con- 

 siderable dissection being possible without 

 leakage. In case the ink runs on to the tissues, 

 it can be washed off under the hydrant. The 

 brilliant contrast of black and white is of 

 course obvious. 



A particularly instructive study can be made 

 by injecting the venous system of the crayfish. 

 The carapace is removed from a freshly killed 

 specimen, and the gills exposed. The ink is 

 then slowly injected into the ventral sinus of 

 the abdomen. The advancing stream can be 

 followed from the different parts of the body 

 (well seen in the transparent joints) to the 

 giUs, through them, back to the body wall, and 

 to the pericardial sinus. The picture seen on 

 clearing one of the gills in glycerine has a new 

 interest to the student, he having watched and 

 controlled the process of filling them. 



This method, besides presenting many an- 

 atomical structures from a physiological point 

 of view, has a wide range of application. A 

 truer, safer and more graphic picture is ob- 

 tained by injecting a duct or opening, than 

 could be secured by probing it. This is of 

 value in some animals in tracing the bile and 

 pancreatic duets, as well as those of other 



glands. It has been successfully applied in 

 some cases to formalin material. Thus the 

 stomach and radial canals of Gonionemus 

 medusa can be demonstrated very well, as can 

 also the pharynx of Amphioxus and its rela- 

 tion to the atrial cavity. Formalin specimens 

 of tapeworm show the longitudinal and con- 

 necting excretory canals very clearly. The 

 living earthworm is very resistant to injec- 

 tions of the blood vessels, a point easily corre- 

 lated with the fact that on cutting the worm, 

 contraction of the vessels prevents bleeding to 

 death. In the grasshopper, the connections 

 between the alimentary canal and gastric ceca 

 can be well shown by injection per os. In some 

 cases water serves the purpose of the ink, as in 

 studying the path of the water in the nasal 

 aperture of the dogfish, or the change of the 

 relations of the parts of the digestive tract 

 when full and empty, or the resistance their 

 inner folds presents to the passage of the 

 food. 



In these injections it should be borne in 

 mind that the process is the part desired, not 

 necessarily the finished product. Further- 

 more, the student should realize that the con- 

 dition of the preserved specimen merely repre- 

 sents one set of conditions in the life of the 

 animal, and the injection should therefore be 

 considered as showing graphically the physio- 

 logical condition of the animal at the time 

 of death only, with such subsequent changes 

 as naturally follow. This is well shown by the 

 difFerent amounts of ink flowing into each 

 vessel, and the ease with which they are filled. 

 The details noted above, while probably in- 

 cluding points now in use in many labora- 

 tories, are given here, as we have found that 

 the use of this technique has given the ele- 

 mentary student a simple means of studying, 

 in the animals dissected in the laboratory, 

 some of the more fundamental problems of the 

 dynamics of organs. 



Eaphael Isaacs 



University of Cincinnati 



THE POISONOUS CHARACTER OF ROSE 

 CHAFERS 



I WAS particularly interested in the article 

 on this subject in Science, January 28, 1916, 



