150 SPECIAL PHYSIOLOGY. 



organisms of a gymnoplastic type, such as the compound amoebiform 

 particles of the Spongida, and the various Rhizopoda, such as the 

 Rotalia, the Actinophrys, and the simple Amoeba itself, and lastly, in 

 the still lower Gregarinida. In all these cases, there is noticed a 

 retraction of a soft tissue in certain directions, accompanied by its 

 extension in other directions; this is the essential character of muscu- 

 lar contraction, even in the highest organized fibre. In the more 

 perfect contractile cells, there probably occurs an approximation of 

 true sarcous elements or particles, filling the entire cell; but in the 

 simpler animals above mentioned, as in the Amoeba, for example, the 

 movement is confined to the outer firmer layer of amorphous sarco- 

 dous substances, the inner portions being semifluid or fluid. All the 

 preceding movements, like muscular contraction, can be excited by 

 electrical, mechanical, or chemical stimuli. 



Movements yet more obscure have been seen in mere masses of pro- 

 toplasm not organized into the distinct cell form, either cystoplastic or 

 fymrioplastic, but merely irregularly aggregated around a nucleus, 

 uch are the budding movements which have been observed in the 

 lymph-corpuscles, and also in the little stellate masses of nucleated 

 protoplasm, known as the connective tissue corpuscles, which, in the 

 frog, especially in the corner of the eye, have been seen to extend 

 themselves in various directions. They are excitable by electrical and 

 mechanical stimuli, and, in the case of the cornea! corpuscles, even 

 through the nerves. The curious movements which take place in the 

 pigmentary contents of the colored cells of the frog's skin, also seem 

 only to be explicable on the supposition of the occurrence of like pro- 

 toplasmic movements. 



However simple these sarcodous and protoplasmic motions may be, 

 they are all similar, or at least allied, to those of the sarcous elements 

 of muscular tissue, and the dependence of all on a common vital prop- 

 erty seems undoubted, though it may be sometimes actively, and at 

 others obscurely, manifested. Retraction and extension, in different 

 directions, always occur; but these movements are sometimes rapid, 

 and sometimes slow; sometimes they are neuro-rnotor, and sometimes 

 idio-motor. If the ciliary motion be included in the same category, 

 its extreme rapidity, and its rhythmic and combined character, appar- 

 ently irrespective of nervous influence, are quite peculiar. 



Vegetable Motion. In the vegetable kingdom two kinds of movements have 

 been observed. Thus, for example, the motions of the leaves of the sensitive 

 plant, of the fly-catching plant, of the stamens of the berberry and other 

 flowers, and of the bifid stigma of the mimosa, may be due to physical 

 changes of an osmotic character, causing a filling or emptying of certain cells; 

 or, as is alleged, in the case of the stamens of the centaurea, the movements 

 may be owing to the action of a true contractile tissue, vegetable sarcode, or 



Erotoplasmic substance, contained in a cell (Cohn). The rapid motions of the 

 irtilizing spiral filaments, known as spermatozoids, in the ferns, lycopodiums, 

 and mosses, seem to be analogous, though this is not certain, to the ciliary 

 motions of the singly-ciliated infusoria. The motions of the algaceous volvo- 

 cinse, desmidise, and others, are almost certainly protoplasmic. Lastly, the 

 remarkable and well-known movements of the contents of certain cells in the 

 vallisneria, chara, and other plants, are of a protoplasmic character : in these 

 cases, globules of chlorophyll, and other minute particles, are seen to move 



