192 



THE CELL AND PROTOPLASM 



toplasm scatter thronji'liont the medium, no 

 films appear, and no vacuoles are formed 

 (Fig. 3). 



As a matter of fact it is logical to sup- 

 pose that within cells reactions similar to 

 blood clotting may occur. For practically 

 all cells of the vertebrate animal contain 

 substances important in blood clotting. 

 Thus, for example, nniscle protoplasm can 



of the sea-urchin egg a mere trace of cal- 

 cium is sufficient to initiate the reaction. 

 Over 100 times as much magnesium is nec- 

 essary to produce the same result (Heil- 

 brunn 1934). This is a point to which I 

 shall return later. 



I have stated that I regard the surface 

 precipitation reaction and the vacuolization 

 reaction as akin to blood clotting. More- 



Fig. 



A, nonnal suiface preeipitatioii leai-tion in 

 crushed in .32 M 



produce as much or more thromlun than 

 an equal quantity of blood. 



It is not my intention at the present 

 time to discuss the attemi)ts we have made 

 to in(juii-e into the details of the surface 

 precipitation reaction. The subject is a 

 complex and a difficult one and progress 

 has been slow. One ])oint I should like to 

 emphasize because of its biological sig- 

 nificance. Althougli sti-ontium is about 

 as effective as calcium in pi-onioling the 

 surface preci|)itfition reaction, Ihe magne- 

 sium ion is far k\ss ]H)tent. In the case 



aicnlor. V>, aliSL'iu-e uf the reaetiuii wlu'ii eells are 

 sodium oxalate. 



over, I believe that an incipient reaction 

 of til is sort occurs whenever a cell is stimu- 

 lated or aroused to activity. Api^ai-ently 

 tlie intei'ior of the living cell contains little 

 or no free calcium. AVhen. however, a cell 

 is stimulated in one way oi' another, I be- 

 lieve that cjilcinni is i-eh^ased t'l-otu the 

 cortex iind th;i1 1his ini-nshing calcinin ])ro- 

 duces an intcrioi- ('h)tting of protoplasm, 

 just as the injection of free calcium into 

 the blood stream causes the blood thei'e to 

 clot. 



What is the e\idence J'or this theory? 



