860 SUMMARY OF CUBRENT RESEARCHES RELATING TO 



protoplasm is bounded by finer integuments, as in ordinary vegetable 

 cells, we have circulation or rotation. 



Under the head of " General Conditions of Spontaneous Proto- 

 plasmic Movements" there are discussed the influences of (1) tem- 

 perature. The optimum temperature — or that in which the move- 

 ment attains its highest velocity — is generally several degrees lower 

 than the maximum temperature compatible with movement. While 

 great heat is certainly fatal, protoplasm even after freezing does, in 

 certain cases, resume its spontaneous contractions ; and it is not 

 necessary that the thawing should take place very gradually. (2) The 

 imbibition of water has effects similar to that of temperature. There 

 is a maximum and minimum at which spontaneous movements stop, 

 and there is always an optimum. There may be a dry rigor, due to 

 the withdrawal of water by indifferent or diluted solutions. In many 

 cases the slow increase of concentration is accompanied by an 

 accommodation of the protoplasm to the solutions. (3) Without 

 oxygen spontaneous movements can never go on for more than some 

 hours at the most. It is clear that living protoplasm enters into 

 chemical union with the surrounding media, and the oxygen thus 

 taken up is probably used for the formation of carbonic acid. 

 (4) Poisons are next dealt with, and diluted alkalies or acids proved 

 to be injurious. Carbonic acid, ether, or chloroform cause temporary 

 or permanent coagulations. Like the contractile substance of mus- 

 cular fibres, many kinds of protoplasm are poisoned by veratrin. 



Artificial stimuli are dealt with as (1) electrical, (2) thermal, 

 (3) luminous, (4) mechanical, and (5) chemical. 



"No theory of protoplasmic movements, leading back to their 

 elementary physical and chemical processes, can be deduced from the 

 hitherto collected facts." As we must start with the acknowledged 

 fact that "each smallest microscopically distinguishable particle of 

 every contractile protoplasmic mass is capable of independent move- 

 ments," it follows that " the movement as a whole is the result of 

 changes of form of these very small elements," the nature and cause 

 of these being provisionally undetermined. There is no reason for 

 supposing that what we can see with the Microscope are the contractile 

 elements themselves ; these are, doubtless, molecular in size, in form 

 sjjherical when excited, and elongated when not so ; these hypothetical 

 contractile elements may be called " Inotagmata." Spheres of naked 

 protoplasm appear after excitation, and this may be explained by the 

 simultaneous assumption of a spherical form by the inotagmata ; the 

 protrusion of processes may be imagined as due to the relaxation 

 (lengthening) of parts of a protoplasmic mass ; rotation takes place 

 when the inotagmata of the moving layers are distributed " with their 

 long axes parallel to the direction of the movement and a forward 

 movement of the spontaneous stimulus takes place in this direction. 

 The moving protoplasm creeps in this manner over the motionless 

 cortical layer just as a snail's foot over the surface upon which it is 

 crawling." 



The author throws out some hints for further investigations into 

 the mechanism of the changes in form of the smallest component 



