SALT AND WATER IN LIFE AND GROWTH 



117 



On the other hand there are cells in which an enveloping 

 membrane is not formed automatically. These cells are 

 surrounded by a membrane, but if it is broken, it fails to 

 regenerate, and the cells disintegrate. To this type belong 

 the red blood cells. If their membrane is broken the red 

 hemoglobin in the cell flows out; no repair is possible. One 



Fig. 34. Microscopic View of a Root Hair of Hydrocharis and Oil 



Drops Squeezed from It 



Droplets squeezed from the tender root hair of Hydrocharis, on contact 

 with water in which they float, immediately surround themselves with a 

 semi-permeable membrane as demonstrated by the fact that they shrink in 

 concentrated salt solutions and swell dilute ones, just as the artificial 

 cell made of gelatin shown in Figure 32. (Magnified 150 times.) 



may assume that this cell membrane was also originally 

 formed by contact of two substances, probably in the bone- 

 marrow where all blood cells originate. The blood into 

 which the cells pass later is not capable of generating the 

 membrane when in contact with the contents of the blood 

 cell; consequently, regeneration of the blood cells in the 

 blood itself does not occur. 



