724 



CELL PENETRATION BY ACIDS. 



The crushed regions about the threads were almost instantly changed 

 to a pink color by acids, but the central part gave penetration times 

 agreeing absolutely with those found for control pieces devoid of 

 ligatures. With a little practice, the strip of tissue could be adjusted 

 without introducing any twist. It was found that these strips of 

 mantle tissue could in all cases support, over the period involved 

 in an experiment, a mass of about 50 gm. Beyond 55 gm., tearing 

 effects became evident. 



Fig. 1. Side view of device for subjecting to tension, in an acid bath, A, a strip of 

 tissue cut from the mantle fold of Chromodoris. T, tissue; a, ligature made fast 

 to glass rod (£>); h, another ligature passing under hook on end of glass rod; 

 and c, smooth metal groove (greased) , over which ligature from b passes to the 

 mass m. 



The acid chosen for most of the measurements was dichloroacetic, 

 since up to 30 or 40 gm. tension the stronger mineral acids, with 

 higher rates of penetration, give figures which could not always be 

 relied upon as different from those obtained with unstretched tissue. 

 With dichloroacetic, however, the effect of stretching was easily 

 shown. 



Experiment 9.26a. — Mantle tissue from a Chromodoris 8.5 cm. long; 0.01 N 

 dichloroacetic acid; 25°C. 



(a) Control, unstretched, penetration time 



{h) With a mass of 10 gm. attached, penetration time 

 (c) " " " " 20 " " " 



Id) " " " " 40 " " " 



tni7i. 

 6.0 

 5.5 

 3.7 

 2.8 



