THE VITAL PHENOMENA OF CELLS 25 



tution, chief among them being proteids, fats and carbohydrates. But from 

 this raw material the animal body has the power of forming many new sub- 

 stances, notably living protoplasm, by a true synthesis. 



Besides the substances just mentioned the animal cell, like the plant cell, 

 requires certain mineral compounds in order that it may develop fully and 

 accomplish its functions in a normal manner. Thus observation on the Meta- 

 zoa has proved that the animal body is continually giving off such substances 

 in its excretions, and would necessarily become impoverished in this respect 

 if the supply were not sufficient. Even in grown animals very profound 

 disturbances ensue as a consequence of such failure of mineral substances, 

 which ultimately end in death. The growing body has a relatively much 

 greater need of inorganic compounds, for such substances are absolutely 

 necessary for the construction of its organs. 



Among the mineral substances contained in the fluids of the animal body 

 common salt (NaCl) comes first in order of quantity. A solution of common 

 salt alone, of a strength corresponding "to its concentration in these fluids 

 (0.6-0.9 per cent), is in fact sufficient to maintain a frog's muscle or a frog's 

 heart in functional condition for a long time after its removal from the body, 

 whereas an exsected heart will not beat in a solution where NaCl is wanting 

 (Lingle). 



In a solution containing only NaCl, however, the contractions of the heart 

 gradually cease, although they may be roused again by the addition of CaCU 

 in small quantity. The addition of KC1 is likewise beneficial; but whereas 

 the Ca salt is favorable to the contraction of the heart, the K salt appears 

 to be important for its relaxation. The heart beats best, therefore, in a nutri- 

 ent fluid in which are contained Ca and K as well as Na (Ringer, Howell and- 

 several other authors). 1 



Analogous phenomena appear in other organs. A skeletal muscle of the frog 

 remains alive outside the body longer if CaCl 2 is added to the NaCl solution. 

 It is asserted, at least for smooth muscles, that the Ca salt favors the contrac- 

 tion process, and KC1 the relaxation, just as in the heart. The egg of Fundulus 

 develops in NaCl solution only when CaCl 2 is added (Loeb). 



In the present state of our knowledge of this subject it would be premature 

 to conclude that the metals just discussed have the same sweeping importance 

 for all animal cells. As a matter of fact data are at hand which show that such 

 a generalization is not warranted. Thus the vibration of flagella e. g., in the 

 spermatozoa and cilia of both vertebrates and invertebrates, is entirely inde- 

 pendent of NaCl in the surrounding fluid. The same is true of the contractile 

 stalk of Vorticella (Fig. 28) and related Protozoa (Overton). In very young 

 larvae of Arenicola cristata solutions containing CaCl 2 favor muscular move- 

 ments, while solutions containing MgCL favor ciliary movements. Pure NaCl 

 solutions are much more harmful for the latter than for muscular movements; 

 Na-free solutions stop muscular movements, whereas cilia remain active in 

 these, and are quite unaffected by pure CaCl 2 or MgCl 2 (Lingle). In this con- 

 nection should be mentioned also the facts brought out by Goldberger that cer- 



1 A solution especially well adapted for feeding an excised mammalian heart is the fol- 

 lowing: eight per cent NaCl, 0.075 per cent KC1, 0.1 per cent CaCl 2 , 0.1 per cent NHCO 3 , 

 and saturated with oxygen. (Compare the composition of the blood ash, Chapter V.) 



