THEIR CAUSES, NATURE, AND PREVENTION. 173 



Excess of salt is highly injurious, interfering as it does with 

 the skin glands, and with the blood, inducing important skin 

 diseases — e.g., scurvy in man and eczema in certain animals, 

 particularly in dogs. 



That 'potash is necessary is proved by the fact of its forming 

 a constituent part of the material food of animals, viz., veget- 

 ables. Deficiency in this salt means impaired tissue nutrition; 

 excess of it means excessive fluidity of the blood, increased 

 activity of the kidneys, by which it is excreted, and dropsies. 

 If the excess persists, defibrination of the blood follows and 

 important forms of skin eruption are produced ; the kidneys too 

 become organically deranged. 



The ]}hosphates are absolutely necessary for the building up 

 and nourishment of the bones and the teeth ; and if they are not 

 supplied in due quantity the former become soft and thus you 

 have produced the various forms of bone-softening, such as 

 rickets and a tendency to fractures, as is sometimes seen in 

 pregnant mares. Moreover, the teeth are imperfectly or slowly 

 developed and when developed tend to decay, and thus you 

 have the late dentition (cutting of teeth) common to animals 

 reared on poor lands and the cases of rotten teeth (caries) 

 which are so often seen under similar conditions. 



Phosphorus is a constituent of nerve matter, and neither can 

 growth go on nor can the functions of the brain be performed 

 without it ; and it must be remembered that animals cannot 

 make up for deficiency in phosphorus in their ordinary food in 

 the same way as man does by eating fish. 



But while phosphorus in due proportion is necessary and 

 beneficial not only it, but phosphates also, in my opinion, may 

 become baneful. Physiologically we know that phosphorus 

 possesses the property, if given in excess, of dissolving and 

 breaking up the blood cells, of causing very rapid fatty degene- 

 ration of the coats of the blood-vessels and of such important 

 organs as the liver and of degrading the colloids of the blood : 

 as a result of this, we get spontaneous flowing out of the 

 blood (haemorrhages) into the tissues, and the passing out of 

 albumen and broken-up red cells, with their colouring matter, 

 with the urine. Superphosphate of lime also possesses the same 

 properties, as was well illustrated some years ago in the case 

 of cattle depastured on land near Liverpool which had been 

 recently topdressed with this agent ; the case came under the 

 observation of Mr Welsby, F.R.C.V.S., West Derby. 



"Without iron no animal could exist for one moment , and 

 small though its quantity in proportion to the other elements 

 of the blood it yet performs a most important function, viz., 

 the carrying of oxygen to the tissues ; the effects of the with- 

 drawal or non-assimilation of iron are quickly seen in the 



