OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 171 



manner that its meslies become wider. It is, however, quite 

 probable that the interstitial substance is a product of the 

 intracellular network. 



(b) The epithelial cells lining the sweat-gland tubes — I refer 

 to the coiled part, not the duct — is in sections of skin, hardened 

 in a mixture of chromic acid and spirit, or also spirit alone, the 

 former being however preferable, composed of a substance 

 which is distinctly longitudinally striated. This striation, when 

 examined with a high power, is seen to be due to the intracellu- 

 lar network consisting prevalently of longitudinal fibrils. This 

 appearance is, however, presented chiefly by the inner portion of 

 the cell substance ; the other part, containing the nucleus, is 

 of a more uniformly " granular'^ aspect, i.e. the network possess- 

 ing a uniform dense arrangement. The nucleus is spherical, 

 and contains a uniform network ; in some instances I see traces 

 of a " nucleolus " (see fig. 11 of PI. VII), 



Skin of sheep and pig is on account of the large size of the sweat glands 

 a very good object. 



The same cliange of shape of the cells that I have mentioned 

 on the occasion of Lieberkilhn's crypts, dependent on the 

 change of lumen of the gland tube, may be noticed also here. 

 Thus I measure in sweat-gland tubes of skin of ear-lobe of pig 

 as the mean : 



0"05 mm. the diameter of the whole tube, including its mem- 

 brana propria, 



0"019 ram. the diameter of lumen, 



0-01 mm. the height of the lining epithelium, 

 and about O'OOS mm. the thickness of muscular coat and membrana 

 propria (see fig. 11). 



In another instance I measure : 



0'076 mm. the diameter of the whole tube, 



0'03 mm. the diameter of lumen, 



about 0*005 mm. the height of tlie lining epithelium, 

 and about 0'002 mm. the thickness of both muscular coat and membrana 

 propria together. 



We find, therefore, in the latter instance in a tube with a 

 greatly distended lumen (0-03 mm. as against 0.019 mm. of the 

 former case) an epithelium correspondingly shortened (0'005 m. 

 as against O'Ol mm. of the former case). 



November, 1878. 



