25G ELASTIN. GROUND SUBSTANCE. [BOOK I. 



Prepara- The lig amentum nuchae of the ox, horse, or still 



tionofEias- better of the giraffe, is cut into thin slices, which are 

 tin - boiled in ether and in alcohol, and then for at least 36 



hours in water. The two first of these reagents free the tissue from 

 fatty matters, whilst the prolonged action of boiling water converts 

 all the collagen into gelatin which passes into solution. The 

 insoluble matter is boiled in strong acetic acid for a long time : 

 then after removal of the acid by water it is boiled in concen- 

 trated solution of caustic soda until the fibres begin to swell. 

 The tissue is then successively heated with dilute acetic acid and 

 with water, and lastly placed for 24 hours in moderately concentrated 

 hydrochloric acid. The substance remaining is washed with water 

 until all acid is removed. It is then found to retain all the original 

 characters of fresh elastic tissue. 9 



Composi- Miiller 1 analysed elastin which he had prepared by 



tion of Elas- following the previously described process and found it 

 tin - to have the following composition. 



(1) (2) J3) (4) 



Carbon 55*47 55*72 55 '55 55*09 



Hydrogen ., 7"54 7*67 711 7'33 



Nitrogen 16*09 1571 16*52 16*43 

 Oxygen 20'90 20*70 20'82. 21*15 



Solubility. So far as is known elastin is not soluble in any liquid 

 which does not decompose it. It is soluble in boiling solution of 

 caustic potash, in cold concentrated suphuric acid, and in concentrated 

 nitric acid. 



It is gradually dissolved when digested with pepsin and with 

 trypsin, the former ferment being more active than the latter 2 . 



Products of When- boiled with sulphuric acid elastin is said to 



decomposition, yield leucine but no tyrosine. 



Connecting or Ground substance of Connective Tissue. 



Absorption When perfectly fresh connective tissue is immersed 



of silver salts f or a f ew minutes in a solution of silver nitrate 



nectS^sub- (' 25 to 1<0 P* c *)' then freed from excess of silver b y 

 stance and washing with distilled water, and afterwards exposed to 



subsequent light, a deposition of metallic silver occurs which 

 reduction. appears to be deposited in the connecting substance 



which is interposed between the various tissue elements. The proto- 

 plasmic elements of the tissue are left perfectly unstained, so that the 

 silver treatment furnishes the histologist with one of the best methods 

 of studying their arrangement. It has been held by many that 

 the absorption of silver, which is afterwards reduced, is a characteristic 



1 Zeitschrift f. rat. Med. Third Series. Vol. x., part 2. 



2 A. Ewald und W. Kuhne, Die Verdanung als histologische MetJiode. 



