252 REACTIONS OF CONNECTIVE TISSUE CELLS. [BOOK I. 



(1) The connective tissue cells are unaffected by iodized serum 

 which constitutes, therefore, the best neutral liquid for their examina- 

 tion. 



Iodized serum is a reagent of very great value to histologists 1 . It 

 is best made by dissolving iodine in the amniotic liquid of the cow ; this 

 fluid is placed in a thin layer in a bottle containing fragments of 

 iodine, with which it is frequently shaken. The iodine gradually dissolves, 

 conferring upon the solution a yellowish tint ; in the course of time iodates 

 are formed which increase the solvent action of the serum on iodine, 

 so that after one or two months a dark brown iodized serum is obtained ; 

 it is when of this colour that it is most serviceable (Ranvier 2 ). 



(2) Solution of perosmic acid (1 to 100) fixes the cells in the 

 form which they present during life, and permits of their being subse- 

 quently stained with picrocarminate of ammonia. 



(3) Silver nitrate (from 0'25 to 0'5 per cent.) is of great 

 use in examining fresh connective tissue. Solutions of this salt 

 acting on the tissue fix the cells in the form which they possess 

 whilst alive, but without colouring them. It is however absorbed by 

 the ground substance and on subsequent exposure to light reduction 

 takes place, so that the unstained cells stand out on a stained back- 

 ground. The treatment with silver does not prevent the subsequent 

 action of certain colouring matters (ammoniacal carmine solution, 

 solution of picrocarmine). 



(4) Solution of gold chloride (1 to 100) is of great use in 

 demonstrating the arrangement of the connective tissue cells of the 

 cornea. It is absorbed by the cells, which it helps to preserve in 

 their natural condition ; the absorbed salt is afterwards reduced and 

 confers upon the cell a reddish violet colour. 



(5) Acetic acid causes the protoplasm to become very transparent, 

 whilst it brings out the nucleus very distinctly. 



The White Fibres of Connective Tissue. Collagen and Gelatin. 



The most abundantly distributed forms of adult connective tissue 

 contain as their principal anatomical element bundles of white fibres, 

 which, as was previously stated, are rendered so transparent by the 

 action of acetic acid, as to be almost invisible. The fibres of which 

 the bundles are made up are connected together by an agglutinating 

 substance, which is soluble in dilute solutions of caustic baryta, or 

 lime. The substance of which the fibrils are composed has received 

 the name of Collagen, from the fact that when subjected to the 

 action of boiling water it is converted into gelatin or glue (KO\\O). 



Prepara- Tendons, being composed almost entirely of the 



tion of Coiia- white fibrils of connective tissue, are best employed in 

 gen. Roiiett's the preparation of collagen. They are cut into thin 

 process. slices and are then soaked in water until all matters 



1 Max Schultze : " Die Anwendung mit lod conservirter thierisclier Fliissigkeiteii 

 als macerirendes und conservirendes Mittel bei histologisclien Untersuchungen." 

 Virchow's Archiv, Vol. xxx. (1864), p. 263. 



8 Ranvier: Traite technique d'Histologie, Vol. i., p. 76. 



