518 Dr. Gr. Thin on the Anatomy of 



II., flat cells, which everywhere cover the fibrillary bundles of the 

 former and line the entire system of the latter ; 



III., the cornea-corpuscles of Toynbee and Virchow ; and, 



IV., the nerve-structures of the tissue. 



The cornea-corpuscles and the nerves lie free in the canals and cavities, 

 and between them and the epithelium there is a fluid-filled space which 

 permits the passage of lymph-corpuscles. 



It is therefore proper to regard the canals, cavities, and inter- 

 fibrillary spaces as forming a continuous and integral part of the lym- 

 phatic system, the latter having to the former the same relation that 

 blood-capillaries have to the veins. 



The junction of the flat cells of the fibrillary substance with the 

 epithelium of the surface justifies the inference that the intercellular 

 spaces in the anterior epithelium of the cornea communicate with the 

 lymph-spaces in the ground-substance, and that the position of nerve- 

 fibrillae between the epithelium is a continuation of the similar relation 

 that has been demonstrated in the substance of the structure. 



It is a reasonable hypothesis that what can be definitely established 

 for the cornea holds good for the other forms of connective tissue. 



I have accordingly submitted tendon to an examination by different 

 methods, with the view of obtaining evidence of the existence in that 

 structure of cells other than those arranged longitudinally between the 

 bundles, the nature of which has lately been carefully investigated by 

 Boll, Spina, Ranvier, and others. 



If the tendo Achillis of a frog, or the tendons of a mouse's tail, fixed 

 according to the ingenious method described by Banvier in his first 

 paper*, are treated by nitrate of silver, care being taken to avoid friction 

 of any kind, it is found that every part of the free surface of the bundles 

 is covered by a continuous epithelium. In the tendo Achillis of the frog 

 I have seen lymphatic capillaries distributed over this surface ; and the 

 epithelial markings can be traced from the cells covering the bundles 

 into those of the vessels. A preparation from the tail of the mouse, 

 showing this epithelium, is represented in fig. 4, Plate IX. 



If sections of tendon are placed for several hours in a strong solution 

 of extract of logwood and alum, and the dye then washed out by concen- 

 trated acetic acid, it is found that while the fibrillary substance becomes 

 clear and transparent, the nuclei retain their colour. This is best done 

 under a cover-glass and under the microscope, as the effect of the acid, 

 if kept too long in contact with the preparation, is to discolour the 

 nuclei also ; the weight of the covering-glass is sufficient to prevent the 

 otherwise invariable distortion of the preparation by the acid. If the 

 preparation is intended to be permanent, all traces of the acid must be 

 removed by a current of distilled water. 



The effect of this treatment is to show that there exists in tendon a 

 * Archives de Physiologie, 1869. 



