DISEASES OF THE HEART. — ATROPHY. 



273 



of the heart, which manifests itself in thinness and atony of the 

 muscular substance as a whole, and hence as a uniform atrophy 

 of the organ. Besides this general form, we may have partial 

 atrophy — atrophy confined to the outermost or innermost layers 

 of tlie muscular coat, sometimes indeed limited to circumscribed 

 patches ; these partial atrophies being due to local causes. 



Whether tlie change be partial or general, the muscular fibres 

 grow thinner, more slender, and may even disappear entirely. 

 Tliis most important result of atrophy presents itself under 

 variously modified histological forms, which may be classed in 

 as many distinct .groups. 



§ 237. (1) Broim atrophy is characterised, as its anme indi- 

 cates, by a change in the colour of the muscular tissue, which 

 assumes a rust^^-brown or dark ochry hue, coincidentlv with its 

 diminution in bulk. This peculiar phenomenon is caused by the 

 deposit of a yellow, granular pigment in the interior of the fibres. 

 It may either be uniformly distributed throughout the contractile 

 substance, or the granules may be heaped up in fine lines be- 

 tween the primitive fibrlllai and around the nuclei (fig. ^C)) ; 

 their source is unknown ; we cannot tell whether 

 they are simply the proper pigment of the mus- 

 cular fibre condensed, or whether the colouring- 

 matter of the blood has a share in their produc- 

 tion. Brown atrophy is always general. It is 

 most common in connexion with senile maras- 

 mus, wasting from inanition, the tuberculous 

 and cancerous cachexia?. 



§ 238. (2) Yelloic atrophy consists in the 

 transformation of the muscular tissue of the 

 heart into fat. (Cf. § 30 and fig. 7.) In \)V0- 

 portlon as the deposit of oil-globules is more 

 al)undant, the muscular filjres grow pale, then 

 yellowlsli, and lastly whitish and bacony. They 

 lose their firmness. The tissue grows friable 

 and rotten ; it breaks down readily under the 

 finger; on the other hand the loss of bulk Is 

 often inconsiderable. 



Yellow atrophy contrasts with the brown variety in the 

 rapidity of its development. It presents itself under four forms : 



a. As a dlff'use degeneration of the entire muscular substance 



18 



Fig. 8(5. 



Brown atrophy of 

 muscular fibres 

 of the heart. 

 Shred of a mus- 

 cular layer ex- 

 hibiting pig. 

 ment - granules 

 in the interior 

 of the primitive 

 fasciculi. -:-,}-. 



