504 



SCIENCE 



[N. S. Vol. L. No. 1300 



experimental cellfibrin tissue; we shall men- 

 tion here a few of the results obtained so far. 



(a) The influence of the temperature is 

 very marked. The temperature coefficient 

 seems to be such as might be expected, if 

 wound healing depended upon chemical pro- 

 cesses. While regeneration takes place stead- 

 ily even in the ice chest at a temperature of 

 from 6-10°, the outgrowth is much more 

 rapid at a temperature of about 20°. Here 

 however also secondary changes take place 

 much more rapidly in the outgrowing cells. 



(&) The depth of the layer of blood serum 

 covering the wound or piece of cellfibrin 

 does not seem to influence the rapidity of the 

 healing process. This seems to indicate that 

 the quantity of oxygen supplied is sufficient, 

 even if a layer of serum about 10 mm. deep 

 separates the tissue from the oxygen of the 

 atmosphere. The amount of free oxygen was 

 still fiorther diminished in experiments made 

 by Miss Clinton. Hydrogen passed through 

 the blood serum for one hour previous to the 

 introduction of the tissue into the serum. 

 This was followed by a second period lasting 

 fifteen minutes in which again hydrogen was 

 carried through the serum. Even imder these 

 conditions outgrowth took place from pieces 

 of cellfibrin previously placed on cover glasses. 



(c) In a third set of experiments we com- 

 pared the intensity of tissue movements in 

 tissue growing in or against the direction of 

 gravity. The tissue was held in a vertical 

 position on the cover glass. We found that 

 the tissues can grow out against the direction 

 of gravity as well or almost as well as in the 

 opposite direction. The average intensity of 

 outgrowth is probably somewhat greater in 

 the direction of gravity than in the opposite 

 direction. 



(d) If we observe tissue growing towards 

 each other from different parts of a wound, 

 or from two separate pieces of cellfibrin placed 

 near each other, we find that the cells coming 

 from opposite directions intermingle quite 

 freely with each other. There is apparently 

 no repellent action exerted by one sheet of 

 tissue upon the movements of the others. It 

 is evidently not the products of metabolism of 



certain cells which induce the cells to become 

 active and to leave the position in which they 

 had been at rest. 



(e) By using our method it is possible to 

 alter experimentally the base on which the 

 tissue moves. Thus we can substitute a sur- 

 face of paraffin, vaselin, coagulated ■ egg or 

 agar for glass or cellfibrin tissue. It is of 

 considerable theoretical interest to determine 

 the character of ameloid movements on sub- 

 stances like paraffin. We find that even on 

 paraffin and vaselin an excellent outgrowth 

 of tissue can take place, although the physical 

 properties of these substances modify in some 

 respects the behavior of the tissue cells. On 

 coagidated egg and agar outgrowth takes 

 place likewise but secondarily osmotic or 

 chemical factors may come into play and 

 injure the cells. 



(/) We have begun the study of the effect 

 of various inorganic substances, particularly 

 of constituents of the blood and seawater on 

 the movement of cellfibrin tissue in wound 

 healing, and on ameboid movement in gen- 

 eral. According to their effect on the tissue 

 movements, we can arrange the various sub- 

 stances in the following order: (1) 2/3-1/2 

 m NaCl, (2) 2/3-1/2 m KCl, (3) 1/2 m CaCl,, 

 (4) m/3 Na, IIP04, (6) 5/8 m N H,C1, (6) 

 m/3 ISTa H,' P 04, (7) H^O. NaCl is the 

 least and N'h^CI, Na H„ P 0.4 and H„0 are 

 most injurious. In the latter solutions no 

 distinct outgrowth takes place. How far cer- 

 tain variable factors as the amount of blood 

 serum adherent to the tissue or bacterial in- 

 fection may modify the results will have to 

 be determined in further experiments. 



Dilution of the solution within certain 

 limits is not incompatible with outgrowth. 

 Thus outgrowth can be readily obtained in a 

 solution of 5 c.c. 5/8 m NaCl + 3 c.c. H^O ; ad- 

 dition of as much as 0.5 c.c. of a m/100 HCl 

 or ISTaOH solution to 5 c.c. 5/8 m N'aCl like- 

 wise permits frequently the outgrowth of 

 tissue. 



We wish to express our thanks to Mr. 

 Julian P. Scott, who assisted us in these 

 experiments. 



Leo Loeb 



