CHAP. IX.] THE CONTRACTILE TISSUES. 325 



careful neutralization) to 45* C. This body is not myosin, being dis- 

 tinguished from it by its insolubility in weak solutions of NaCl 1 . 



2. An alkaline (potassium) albuminate, which is only precipi- 

 tated when the reaction is made strongly acid. 



3. Albumin apparently identical with serum-albumin, and 

 coagulating, like it, at a temperature between 70 and 75 C. and not 

 coagulated by the addition of ether. This proteid is much more 

 abundant than either the first or second mentioned. 



The great majority of the constituents to be discussed in the 

 sequel are contained in the muscle serum ; they will, however, for 

 convenience, be considered under separate headings. 



The Haemoglobin of Muscles. 



We have already stated that certain of the voluntary muscles are 

 distinguished by their red colour, due to the presence of haemoglobin 

 which colours the contents of the sarcolemma. In warm-blooded 

 animals, indeed, the majority of muscles are red, whilst in cold- 

 blooded animals frequently the heart is the only red muscle. In 

 certain gasteropod molluscs (Limnaeus and Paludina) Lankester 

 made the remarkable observation that whilst haemoglobin is not 

 present in the blood, it colours the muscular fibres which occur in the 

 walls of the pharynx, these muscles being among the most active in 

 the body. 



Wherever haemoglobin occurs in the substance of muscle it colours 

 the plasma and not the anisotropous sarcous elements ; when the 

 plasma coagulates, a portion of the colouring matter adheres to the 

 myosin, whilst a portion remains in solution in the muscle serum. 

 To demonstrate the presence of haemoglobin in muscle, the blood- 

 vessels are washed out with salt solution, and thereafter the blood- 

 free muscle is held between a light and the slit of the spectroscope. 

 The muscular portion of the diaphragm of the rabbit lends itself 

 particularly well to this observation. Crystals of haemin may by 

 suitable treatment be obtained from the red muscles, or from the 

 plasma which they yield (Kiilme). 



NITROGENOUS (NON-PROTEID) ORGANIC CONSTITUENTS OF MUSCLE. 



Extract of When finely divided dead muscle is repeatedly 



meat. treated with cold water, this liquid dissolves the whole 



of the constituents of the muscle serum and, in addition, 

 perhaps, soluble matters derived from the insoluble anisotropous 

 sarcous elements. The solution thus obtained has a red colour due 

 to the haemoglobin extracted from the muscular fibres and (unless 

 the blood-vessels have been thoroughly washed out with salt solution) 

 derived from the blood contained in the vessels of the tissue. 



1 The reader is referred for some recent observations on the proteids of Muscle to a 

 paper by Demant entitled " Beitrag zur Chemie der Muskeln." Zeitschrift f. physiol. 

 Chemle, 1879, p. 241. 



