62 ANIMAL PHYSIOLOGY. [LESSON 21. 



It was to this particular principle of exudation of the plastic 

 lymph, whereby a new tissue may be formed without the agency of 

 development by cells, that the comparison was intended to apply. 



365. Examined by the microscope, it will be seen that the usual 

 mode by which tissues are constructed out of fibrine, consists in a 

 tissue of densely matted fibres, which cross each other in every pos- 

 sible direction ; this can be well seen in the Crassamentum, or clot 

 (the solid, colored portion) of human blood, or of the blood of any 

 other animal. The clot should be hardened by boiling, and thin 

 slices of it made with a sharp razor ; the fibres (fibrillated) of fibrine 

 will be clearly seen, and in their meshes, or interstices, the red cor- 

 puscles. The arrangement, however, of the fibrine is still better seen 

 in the Bufy coat, or fluid portion of the blood which arises above 

 the surface of the clot. 



366. This mode of tissue forming is not limited to the process of 

 repair ; there are certain distinct tissues in the Animal Kingdom, 

 always, and alone formed on this principle. 



If the Hen's egg be boiled moderately hard, the white will dis- 

 play a tough, semi-transparent membrane in which it is enclosed, and 

 which separates it from the shell : it is called Membrana putaminis. 



367. If this membrane be macerated in water for a few days, it 

 may then be separated into layers many of which will be found to 

 enter into its composition ; examine one layer by the microscope, 



and an appearance will present itself like 

 Fig. 90. Now drop a piece of the shell 

 into Acetic Acid, which will quickly re- 

 move the Carbonate of lime, with which 

 the animal membrane has been consoli- 

 dated ; examine this membrane with the 

 microscope, and it will then appear that 

 the animal basis of the egg shell is a sim- 



^^^^^^*^^ pie matted tissue of fibrillated fibrine, 

 Membrana putaminis. 



ofiering its meshes as receptacles for the 

 deposition of the mineral matter. 



Here, then, is an animal membrane destitute of blood-vessels, 

 and wholly formed by the consolidation of Fibrinous elements. 



368. Wounds that are said to heal (in surgical language) by " the 

 first intention," are really knit together by the plasticity of the co- 

 agulable lymph, as the liquor sanguinis of the blood is called ; in 

 other words, lymph is thrown out from each lip of the wound, and 

 extending across to, and joining the other lip, the lymph fibrillates 



