1883.] 



MICROSCOPICAL JOURNAL. 



1 1 



outer or freely projecting portions of 

 the cilia are driven in the opposite di- 

 rection, each ciliuni representing a 

 lever, the short arm of which is within 

 the cell in connection with the intro- 

 cellular network, the long arm being 

 the freely projecting part, and the 

 fulcrum, or fixed point, lying in the 

 membrane covering the free cell 

 borders. When, in the next moment, 

 the contraction of the introcellular 

 net-work ceases, the cilia move again 

 in the opposite direction. These two 

 phases would correspond to the to- 

 and-fro movement of the cilia." While 

 it is quite possible to account for the 

 simple variety of movement in the 

 above manner, it does not seem to 

 cover the case of the three or four 

 more complex movements. A theory 

 has however been advanced by En- 

 gelmann, applicable to all cases, and 

 in my mind the most plausible of any 

 thus far proposed. I cannot, there- 

 fore, do better than to quote his words 

 in regard to the " Theory of Ciliary 

 Motion," with which I fully agree : — 

 *' From the incomplete condition of our 

 knowledge, and particularly from the 

 deficiency of a closer insight into the 

 chemical processes which play their 

 parts within the cells and cilia, we are 

 furnished with but a single foundation 

 stone upon which to build a theory for 

 ciliary movement. " As in protoplasm, 

 attention is especially directed to a 

 closer analysis of the obvious mechan- 

 ical processes. In this connection, 

 the following short remarks may be 

 sufficient. It is essential that the per- 

 formances displayed in protoplasmic 

 movement should be here brought 

 forward and made use of. We have 

 to admit thereafter that ciliary move- 

 ment issues, in all cases, from exceed- 

 ingly minute elements, contained in 

 the cilia themselves. 



" These minute elements which, in 

 a condition of rest are stretched out, 

 and during contraction approach a 

 spherical form, must be united in a 

 firm arrangement, and all in like sense 

 placed with their long axis parallel to 

 the long axis of the cilium. Such 



an arrangement may be preserved 

 through the simple surface attraction 

 of the elements, by a sufficiently 

 small quantity of the intertegmatic 

 fluids. Indeed one often sees, in con- 

 sequence of the evaporation of the 

 water, hyaline protoplasm, form itself 

 into the finest cilia, or split up into 

 fibrillas. 



" The changes of form in the ino- 

 tagmen constituting a cilium must, as 

 a legitimate consequence, be found to 

 proceed from the base to the point, 

 either rectilinearly upon the surface, 

 or changing from the fore to the back 

 surface of the cilium, (hook-shaped, 

 wave-like motions,) or in a spiral turn, 

 (funnel-shaped motion). The imme- 

 diate cause of the changes of form in 

 the inotagmen, should be sought in 

 the changes in the conditions of dis- 

 tention (quellung zustande) of the 

 same. The cause of this, that is, the 

 physiological irritation, is due to molec- 

 ular proceedings, of a kind not under- 

 stood, starting periodically in the cell 

 protoplasm, or (in the automatically 

 moving cilia, e. g., many spermatozoids ) 

 in the substance of the cilium. There- 

 fore, as the mechanism of ciliary 

 movement is in principle to be re- 

 garded as identical with muscular 

 movement, so, apparently, the pro- 

 ceedings which stimulate movements 

 are identical with nerve incitation." 



Coming now finally to the function 

 of vibratile cilia and ciliary motion, 

 the first thing that strikes us, is the 

 constancy with which cilia are found 

 in connection with the respiratory ap- 

 paratus, from the lowest forms up to 

 man. In the lower types they un- 

 doubtedly act as true respiratory 

 organs, and up to the newt they are 

 found still to retain this position, this 

 creature being known to inhale water 

 by the nostrils and discharge it by the 

 mouth, twelve or fifteen times a min- 

 ute, passing it in this way over the 

 extensive tracts of ciliated epithelium 

 in the nasal passages, mouth, and 

 probably over those of the trachea and 

 Dronchi, although it is not positively 

 known whether the water is drawn 



