78 



MANUAL OF HISTOLOGY. 



Both of these the reception of matters into their interior, and the 

 locomotive propensities of cells furnish us with an insight into a new 

 world of liliputian life. Owing to these properties, the amoeboid cells of 

 such animal fluids as lymph, mucous and serous exudations, may wander 

 out from deep or remote organs in any direction. Cohnheim has fur- 

 nished us lately with some extraordinary results of his observations on 

 these points in regard to inflammation, but we will defer the considera- 

 tion of them until we can enter into it at greater length in another part 

 of our work. We learn, however, from these and the possibility cannot 

 be denied that small, formed particles of zymotic and infecting sub- 

 stances can be taken up by amoeboid cells, and 

 transported by the latter to distant localities in 

 the body, to the imminent danger of, and with at 

 times the greatest inj.ury to the system. 



It seems to us, further, as though a comparison 

 may be instituted between this contractility of 

 the bodies of cells, and another kind of motion 

 observed in certain appendages of the latter. We 

 refer to the small, hair-like formations attached to 

 the surface of various epithelial elements, to which the name cilia has 

 been given, the latter on which they are placed being termed on this 

 account ciliary epithelia (fig. 70). As long as life 

 clings to the part so long are these delicate hairs 

 engaged in a constant and rapid undulating movement. 

 But we will consider this " ciliary motion " more fully 

 further on. 



The nucleus, also, or parts formed from it may, 

 although exceptionally, become contractile in animal 

 cells. But up to the present we are acquainted with 

 really contractile nuclei only among the inverte- 

 -Human sper- brata. The spermatozoa of vertebrates, however (fig. 

 matozoa. 7]^ with their wonderful power of rapid progression, 



afford an example of bodies which have their origin perhaps in the 

 nucleus. These will be discussed more at length presently. 



ijf. 70. Ciliated cells of the 

 mammal, a-d, body of the 

 cell with cilia. 



. 7i 



50. 



Let us now contemplate among the vegetative phenomena of cell-life 

 the growth of this element. 



Like all other organic structures the animal cell possesses the capa- 

 bility of growth, of increase in size, by means of the introduction of new 

 particles among those already composing its body, or, as it is the custom 

 to say, by " intussusception." And in that the most extended use is made 

 of this property throughout the system, we see .consequently that in size, 

 newly formed cells are much smaller than those already arrived at maturity. 

 The enlargement of cells, however, takes place very unequally in the 

 several tissues; in some they usually increase but moderately in size, as, 

 for instance, in certain epithelia, while in others, as in the elements of un- 

 striped muscle, they may undergo an enormous augmentation in volume. 

 These latter are the contractile fibre cells already so frequently referred 

 to. Certain cells, also, as, for instance, those of fatty tissue and cartilage, 

 are often much more minute in the advanced embryo, or infant, than 

 in the same tissue in the adult human body, a fact established many 



