304 



MANUAL OF HISTOLOGY. 



Fig. 294. Human muscle 

 studded with fat-cells, a, 

 muscular fibre ; 6, rows of 

 fat-cells. 



increases enormously in volume at certain times, a fact which depends 

 chiefly on changes in its muscular tissue. The contractile fibre-cells 

 become enlargedto 7-1 1 times their original length, and to 2-5 of their 

 breadth (KoeUiker). Besides this, there takes place, according to the 

 same observer, a reproduction of cells also. 



After parturition a decrease in the size of the contractile cell begins to 

 be apparent, with which it returns in about three 

 weeks to its original dimensions. Fatty infiltra- 

 tion of the substance of the latter during this 

 period is of frequent occurrence, and we may also 

 accept as a certainty the resolution of a certain 

 number of the muscular elements also. 



That there really may be such a thing as a phy- 

 siological hypertrophy of the striped fibres can 

 hardly be doubted any longer since Auerbach's dis- 

 coveries. 



In hypertrophied hearts it was stated by Hepp 

 long ago that thickening up to four times their 

 original size took place in the fibres. It would 

 appear, however, that there is really only a multi- 

 plication of the fibres here (perhaps by longitudinal 

 division). 



Pathological hypertrophies, however, of un- 

 striped muscle, amounting even to the formation of 

 tumours, are of frequent occurrence. They affect 

 parts which are richly supplied with this tissue, 

 such as the oesophagus, stomach, and uterus. Their genesis requires to be 

 made the subject of more accurate investigation than has as yet been the 

 case. That a transformation of connective-tissue cells into contractile 

 elements takes place is at least probable (Aeby, Arnold, Koclliker). 



Finally, we meet with an atrophy of muscle fibres or disappearance of the 

 same. In the first place, this is encountered as a more or less normal pheno- 

 menon in old age. Then, again, it appears more fre- 

 quently under pathological conditions as a diminu- 

 tion in the diameter of the fibre (as in paralysis of 

 various members), combined, to a certain extent, with 

 fatty degeneration of the fibre or development of in- 

 terstitial fat-cells. The latter (fig. 294) have been 

 already discussed ( 122 and 169). If this latter pro- 

 cess proceed to too great length, it may possibly inter- 

 fere at last with the functions of certain portions of 

 muscle through pressure, as, for instance, in the heart. 

 The deposit of small molecules of fat in the interior of 

 fibres is of frequent and normal occurrence when the 

 quantity of the former does not become too great. 

 Thus we meet with it in the muscle of the heart, and 

 in the frog in the muscles of the extremities ( 166). 

 In a greater degree it must be looked upon as a pheno- 

 menon of retrograde development (fig. 295), of patho- 

 logical significance. But, on carefully searching 

 through healthy muscles, we will always encounter 

 certain fibres containing a considerable amount of fat granules of this 

 kind, and not unfrequently also a diminution in thickness, so that it is 



Fig. 295. Fatty de- 

 generation of human 

 muscle fibres. , low 

 degree; 6, a higher; c, 

 the highest degree. 



