284 MANUAL OF HISTOLOGY. 



The sweat-glands are surrounded by a somewhat loose 

 fibrous connective tissue, from, which fibres pass inward and 

 form a closer network between the coils of the gland. Some 

 of the fibres run parallel, and others transversely or obliquely, 

 to the long diameter of the convoluted tube. A large number 

 of lymphoid cells are always present in this interglandular 

 connective tissue. The sweat-glands are richly supplied with 

 blood-vessels. 



The excretory duct passes upward from the gland proper 

 in a more or less vertical direction through the different layers 

 of the skin to its free surface, where it opens with a funnel- 

 shaped orifice. In passing through the corium it pursues a 

 straight or slightly wavy course, and enters the lowest part 

 of the inter-papillary rete. The structure of this part of 

 the excretory duct differs from that of the gland proper, in 

 the shape of the cells, the absence of muscle-fibres, and the 

 presence of a cuticula. This cuticula lines the inner surface 

 of the epithelial coating and limits the lumen of the duct. 

 As the rete Malpighii is entered there are generally two or 

 more layers of cells lining the duct, the number increasing 

 as the rete is approached. The transition from secreting cells 

 to lining cells is gradual, so that the presence of a cuticula 

 decides the nature of the tube. The basement -membrane 

 corresponds in structure with that of the gland proper. The 

 fibres of surrounding connective tissue run parallel with the 

 duct. 



As the duct approaches the rete Malpighii its epithelial 

 cells increase in number and form two or more layers, which 

 are really only a continuation downward of the cells of the 

 rete. When the duct enters the rete it loses its basement- 

 membrane and is formed only of the cells of the mucous layer, 

 which have become more or less flattened and spindle-shaped. 

 The direction of the duct through the rete is sometimes straight 

 and sometimes spiral. 



In passing through the stratum corneum the duct pursues 

 a spiral direction on account of the horizontally flattened cells 

 of this layer (see Fig. 114, /), and the number of spirals pres- 

 ent depends upon its thickness. The largest number is found 

 in the palms of the hands and soles of the feet, where it may 

 amount to twenty or more, whilst on some parts of the body 

 there is not even a single complete spiral. The wall of the 



