MUSCLE. 



507 



organization and properties, but that this simple 

 method of procedure is the one most likely to 

 lead to a true insight and conclusion regarding 

 the anatomy, not only of this but of all elemen- 

 tary structures, becomes every day more evi- 

 dent. Various subsidiary means may doubtless 

 be employed with advantage, such as injections 



the width of others. In general the fibres of 

 the heart are smaller than those of other striped 

 muscles. The varieties in the average bulk in 

 different classes have a close connection with 

 differences of nutrition and of their irritability, 

 which will be reverted to. 



3. Figure. This is subject to some variety, 



and physical and chemical agencies ; but the depending on their number and manner of 

 method which of all others is the least liable to package. Sometimes, as in some parts of In- 

 admit of erroneous interpretations by the ad- sects, they are flattened ; but when they are 

 mixture of artificial elements in which the mind 

 of the inquirer has had a share, is that of em- 

 ploying a power capable of reaching the utmost 

 limits of organization, on examples the most 



isolated, or loosely aggregated, they are more 

 or less cylindrical. In all the cases, however, 

 where many fibres are arranged side by side, 

 as in the Vertebrata, the larger Insects, and 



nearly approaching to their natural state during Crustacea, they are irregularly polygonal, the 

 life. contiguous sides being flattened, evidently from 



There is perhaps no one line of inquiry in the effect of package. Yet some interspaces 

 the whole range of minute anatomy so beset are always left for the passage of bloodvessels, 



with difficulties and sources of error, and 

 therefore so much demanding a cautious study 

 and sagacious discrimination between conflict- 

 ing appearances, as this of the structure of the 

 striped fibre. The following description is 

 substantially the same as that published by me 

 in the Philosophical Transactions, 1840, and 

 which all my subsequent observations have 

 tended to confirm. To that paper I would 

 venture to refer those who may desire to enter 

 at greater length upon the grounds of the view 

 here summarily given. 



1. Length. This varies exceedingly in dif- 

 ferent muscles. The sartorius, the longest in 

 the body, often surpasses two feet in length, 

 and the individual fibres are as long, extending 

 in parallel bundles from end to end. In many 

 others they do not exceed a quarter of an inch ; 

 thus their greatest variety is presented in their 

 length. 



2. Thickness. This should be examined in 

 the uncontracted slate of the fibre, which for 

 this purpose should be removed from the body 

 after all contractility has departed. I have 

 elsewhere* given a table of numerous compa- 

 rative measurements in various animals, and 

 subjoin the following abstract: 



Diameter of the elementary fibres of striped 

 muscle infractions of an English inch. 

 From to 



average of males 355 



Human 



T 5 , 



females 



sso> 



S5, 



2&OJ 



B57 

 as* 

 555 



TO 



Other Mammalia T1 ' U5 T 2 , average 



Birds ........ TSOO 



Reptiles ...... lg ga 



Fish .......... 1753 



Insects ...... 733 



I believe that the average diameter of the 

 fibres in the human female is upwards of a 

 fourth less than in the male, and that the ave- 

 rage of both together is greater than that of 

 other Mammalia; but a more extensive exami- 

 nation is requisite to establish this. Fish have 

 fibres nearly four times thicker than those of 

 Birds, which have the smallest of all animals. 

 Next to Fish come Insects, then Reptiles, then 

 Mammalia. In each of these different classes, 

 however, an extensive range of bulk is observ- 

 able, not only in the different genera, but in the 

 same animal and the same muscle, some fibres 

 being occasionally three, four, or more times 



* Philosophical Transactions, 1840, p. 460. 



nerves, and areolar tissue among and be- 

 tween them. Their form may be most readily 

 displayed by a transverse section of a muscle 

 that has been dried en masse, as long ago shown 

 by Leeuwenhoeck (jig. 286). 



4. Colour. The colour of muscle depends 

 partly on the colour of its elementary fibres, 

 partly on the blood contained in its vessels, 

 and there is strong reason to believe that the 

 colouring matter of both is the same, or nearly 

 so. That the fibres have always a colour of 

 their own is at once evident on inspection 

 under the microscope. It is generally more or 

 less of a reddish-brown, but varies much in 

 different animals and in different muscles, and 

 even in the same muscle according to its state 

 of development and activity. In Reptiles and 

 Fish generally, and in Crustacea, the flesh is 

 white, sometimes pinkish, but in some fishes, 

 as the Gurnard, the gill-muscles are red. These 

 varieties of colourare attended with none of struc- 

 ture. In Birds the colour varies much, being 

 often white and deep red in the same animal, but 

 generally the pectoral muscles are very dark. 



Fig. 286. 



Transverse sections of striped muscle thai had been 

 injected and dried, magnified 70 diameters. 



A, from the Frog. 



B, from the Dog. 



a, a, section of elementary fibres, shewing their 

 angular form and various s.ze. 



b, b, sections of the injected capillaries, shewing 

 the position they occupy among the fibres. 



These figures shew ih greater vascularity of the 

 muscle with the narrower elementary fibres. 



