MACDOUGAL^ACTION OF LIPOIDS IN GROWTH. 51 



the cell and allow the escape of its contents. Whether wall and 

 plasma are equally changed is not shown. It is important to note 

 that such increased permeability results in the stronger solutions 

 without the addition of a salt as in Boas's experiments. 



Increase of the hydrogen-ion concentration did not modify the 

 action of the saponin in the single series of tests carried out as 

 shown below in which thin slices of living tissue were hydrated. 



Solution. Swelling. Time. 



Water 20 per cent. 2 hrs. 



Saponin 0.0051!/ \ o 20 



} 



> 9 10 



KCl ooosil/ J 



HCl o.oosil/ 

 Saponin o.oosilf ) 



The presence of the salt, however, appeared to speed up the 

 process of imbibition and to hasten the shrinkage. 



Sections of living tissue such as the above show a swelling 

 slightly less than that in water when hydrated in acid at PH 2, due 

 presumably to increased permeability. KHO at 0.0 iM also gives a 

 swelling slightly less than water, at PH 12. Such a result would 

 be much more complicated, as the hydroxide may affect lipoids as 

 well as the proteins of the plasma. Sections which increase about 

 75 per cent, in water swell only 31 per cent, in KHO 0.2M, 67 per 

 cent, at o.o^M, and 70 per cent, at 0.0 iM, and the maximum lies near 

 this concentration, a lessening swelling appearing in concentrations 

 of 0.005M. 



Dried sections hydrated in a series of concentrations of HCl 

 which swelled 240 per cent, in water did not reach this figure in 

 HCl 0.0 1 A^ At weaker concentrations no graded series of values 

 was obtained, but increases of 255 to 300 per cent, were measured. 

 These reactions would be similar to hydration values of agar-gelatine 

 biocolloids in which the pentosanic and the albuminous components 

 were nearly equal in quantity. Similar sections which swelled 185 

 per cent, in water increased 200 per cent, in KHO at o.oiN, 250 per 

 cent, in a 0.0057V solution, 210 per cent, in a o.ooiA'^ solution, and 

 gave the same value as water in KHO at 0.0002A''. These hydration 

 reactions are also in consonance with the relative swellings in water 



