580 



SCIENCE 



[N. S. Vol. LIV. No. 1406. 



strong inhibitory action of the perivisceral 

 fluid upon fertilization should occur at the 

 breeding season. As to the action of the der- 

 mal secretion there seems to be hardly any bio- 

 logical significance, since under natural condi- 

 tions neither egg nor sperm encounters such a 

 high concentration of the secretion as suffices 

 to inhibit fertilization. 



Having been engaged in other work, I could 

 not carry out this series of experiments more 

 fully and accurately. But, as I shall not have 

 further opportunity of dealing with this At- 

 lantic species, I have here ventured to commu- 

 nicate this incomplete note, simply with the 

 hope that it may lead to further research on the 

 seasonal changes in the eilects of the " dermal 

 secretion " and the " perivisceral fluid " of the 

 sea-urchin upon the fertilizability of the egg. 

 HmosHi Ohshima 



Princeton University 



SIMPLE METHOD OF BLEEDING RABBITS 



The simplest method of obtaining rabbit's 

 blood, when more than a few drops are neces- 

 sary, is that of bleeding from the median 

 artery of the ear. This vessel stands out 

 prominently and is easy of entrance, if the 

 animal is full grown. As much blood can be 

 taken by this method as directly from the 

 heart, and either a syringe may be used, or a 

 cannula only, with a tube to receive the fluid. 



The chief advantage of bleeding from this 

 vessel is that small quantities of blood (3 c.c. 

 to 5 c.c.) may be obtained at frequent inter- 

 vals (daily, if necessary), each point of entry 

 being successively nearer the base of the ear. 

 Ten or more cubic centimeters may be obtained 

 just as easily. 



It is occasionally found that even when the 

 needle seems to be safely within the artery, 

 a good flow does not follow. This is some- 

 times caused by a plug of skin blocking the 

 passage of the blood, but more often it will be 

 found that there are two smaller arteries in 

 place of the single larger one, with a conse- 

 quently smaller flow in each. Animals which 

 have the single vessel should for this reason 

 be selected. In general, the larger the vessel, 

 the greater is the ease of obtaining blood. 



A sharp needle is essential, because, due to 

 the thickness and toughness of the arterial 



Rabbits 



walls, a somewhat dull point will almost in- 

 variably pass around the vessel rather than 

 into it. A small needle is best because of the 

 smaller puncture it makes, and the conse- 

 quently greater ease of stopping the blood 

 after withdrawal. A 21- to 23-gauge needle 

 has been found by the writer to be most satis- 

 factory. 



Little trouble is experienced in stopping 

 the flow upon withdrawal of the cannula, usu- 

 ally no more than following withdrawal from 

 a vein. Potassium alum will very quickly stop 

 the bleeding where it will not do so naturally. 



The marginal ear vein may also be used in 

 the same way, though it is difficult to obtain 

 more than a cubic centimeter or two there- 

 from on account of the lower pressure and de- 

 creased flow in the veins. The needle must, 

 of course, in all cases be inserted opposite to 

 the direction of the blood flow. 



White rabbits, or rabbits with white ears, 

 are much the most suitable sort for this work 

 for obvious reasons. Injections into and 

 bleedings from ear vessels are greatly facili- 

 tated by placing an electric light below the 

 ear in such a position as to make the ear trans- 

 lucent. If alcohol is applied on a bit of ab- 



