428 ELEMENTARY PROBLEMS IN PHYSIOLOGY. 



To Professor Saclis, tliis porous constitution of protoplasm serves to 

 explain the proi)ert.y of vital turgescence, that is, its power of charg- 

 ing itself with acpieous liquid; — a power which Saclis estimates to be 

 so enormous that living protoplasm may, he believes, be able to con- 

 dense water which it takes into its interstices to less than its normal 

 volume. For the moment it is sufficient for us to understand that to 

 the greatest botanical thinkers, as well as to the greatest animal physi- 

 ologists, the ultimate mechanism by which life is carried on is not as 

 Professor Sachs* puts it, ''slime," but "a very distensible and exceed- 

 ingly fine net-work." 



And now let us try to get a step further by crossing back in thought 

 from plants to animals. At first sight the elementary vital processes 

 of life seem more complicated in the animal than in the plant, but they 

 are on the contrary simpler; for plant protoplasm, though it may be 

 structurally homogeneous, is dynamically polyergic, — it has many en- 

 dowments — whereas in the animal organism there are cases in which a 

 structurehas only one function assigned to it. Of thisthebest examples 

 are to be found within so-called excitable tissues, viz, those which are 

 differentiated for the purpose of producing (along with heat) mechanical 

 work, light, or electi"icity. In the life of the plant these endowments, 

 if enjoyed at all, are enjoyed in common with others. 



By the study therefore of muscle, of light organ and of electrical 

 organ, the vital mechanism is more accessible than by any other ])ortal. 

 About light organs we as yet know little, but the little we do know is 

 of value. Of electrical organs rather more, about muscle a great deal. 



To the case of muscle, Engelmann, one of the best observers and 

 thinkers on the elementary questions which we have now before us, has 

 transferretl the terminology of Niigeli and Pfeffer as descriptive of the 

 mechanism of its contraction. Muscular protoplasm differs from those 

 kinds of living matter to which I have applied the term "polyergic," in 

 possessing a molecular structure comparable with that of a crystal in 

 this respect that each portion of the apparently homogeneous and trans- 

 parent material of which it consists resembles every other. 



With this ultra-microscopical structure, its structure as investigated 

 by the microscope, may be correlated, the central fact being that, just 

 as a muscular fiber can be divided into cylinders by cross-sections, so 

 each such cylinder is made up of an indefinite number of inconceivably 

 minute cylindrical parts, each of which is an epitome of the whole. 

 These Engelmann, following Pfeffer, calls ino-tagmata. So long as life 

 lasts each minute phalanx has the power of keeping its axis parallel 

 with those of its neighbors, and of so acting within its own sphere as 

 to produce, whenever it is awakened from the state of rest to that of 

 activity, a fluxion from poles to equator. In other words, muscle, like 

 plant protoplasm, Qonsists of a stable framework of living catalysing 



" Sachs, Experimental-Physiologie, 1865, p. 443 ; and Lectures 07i the Physiology of 

 riants, English translation, p. 206. 



