MAMMARY GLANDS. 46 i 



25 cubic centimetres of the water to be investigated are mixed with 50 cubic 

 centimetres of concentrated H 2 S04, and titrated with B until a green colour is 

 obtained. This process must be repeated, and on the second occasion the solution 

 B must be allowed to flow in at once, when usually somewhat more indigo solution 

 is required to obtain the green solution. The number of cubic centimetres of B 

 (corresponding to the strength of B, as determined above), indicates the amount of 

 nitric acid present in 25 c.cmtr. of the water investigated. As much as 10 milli- 

 grammes nitric acid have been found in spring- water (Marx, Trommsdorff ). 



Sulphuretted Hydrogen is recognised by its odour ; also by a piece of blotting- 

 paper moistened with alkaline solution of lead becoming brown, when it is held 

 over the boiling water. If it occurs as a compound in the water, sodium nitro- 

 prusside gives a reddish violet colour. 



It is of the greatest importance that drinking water should be free from the 

 presence of organic matter in a state of decomposition. Organic matter in a 

 state of decomposition, and the organisms therewith associated, when introduced 

 into the body, may give rise to fatal maladies, e.g., cholera and typhoid fever. This 

 is the case when the water-supply has been contaminated from water which has 

 percolated from water-closets, privies, and dung-pits. The presence of organic 

 matter may be detected thus (1) A considerable amount of the water is evaporated 

 to dryness in a porcelain vessel, if the residue be heated again a brown or black 

 colour indicates the presence of a considerable amount of organic matter ; and if it 

 contain N, there is an odour of ammonia. Good water treated in this way gives 

 only a light-brown. The presence of micro-organisms may be determined microsco- 

 pically after evaporating a small quantity of the water on a glass-slide. (2) The 

 addition of potassio-gold chloride added to the water gives a black frothy precipitate 

 after long standing. (3) A solution of potassium permanganate, added to the water 

 in a covered jar, gradually becomes decolourised, and a brownish precipitate is 

 formed. 



Water containing much organic matter should never be used as drinking water, 

 and this is especially the case when there is an epidemic of typhoid fever, cholera, 

 or diarrhoea. In all such circumstances, the water ought to be boiled for a long 

 time, whereby the organic germs are killed. The insipid taste of the water after 

 boiling may be corrected by adding a little sugar or lime juice. 



230, Structure and Secretion of the ^Mammary 



Glands. 



About 20 galactoferous ducts open singly upon the surface of the nipple. Each 

 of these, just before it opens on the surface, is provided with an oval dilatation 

 the sinus lacteus. When traced into the gland, the galactoferous ducts divide like 

 the branches of a tree, and a large branch of the duct passes to each lobe of the 

 gland, all the lobes being held together by loose connective-tissue. Only during 

 lactation do all the fine terminations of the ducts communicate with the globular 

 glandular acini. Every gland acinus consists of a membrana propria, surrounded 

 externally with a net-work of branched connective-tissue corpuscles, and lined 

 internally with a somewhat flattened polyhedral layerof nucleated secretory cells (Fig. 

 171.) The size of the lumen of the acini depends upon the secretory activity of the 

 glands ; when it is large it is tilled with milk containing numerous refractive fatty 

 granules. The milk-ducts consist of fibrillar connective- tissue. Some fibres are 

 arranged longitudinally, but the chief mass are disposed circularly, and are permeated 

 externally with elastic fibres, while in the finer ducts, there is a membrana propria 

 continuous with that of the gland acini. The ducts are lined by cylindrical 

 epithelium. 



