90 ABOUT LOBSTERS 



along well within a wide range of temperatures, that is, 

 from a few degrees up to approximately 77° F. A con- 

 tinuous supply of fresh oxygenous water is, however, 

 essential. As will be seen from the following, this in- 

 volves a number of technical difficulties for the fish 

 dealer, especially in warm weather. . . . 



Salt is essential to the lobster's functions, which is 

 why the salt concentration in the lobster's blood has to 

 be constant. In sea water, the salt concentration in the 

 lobster's blood is approximately the same as that of the 

 surrounding water. If the sea water is diluted, for in- 

 stance by adding fresh water, the salts will be washed 

 out of the lobster's blood into the water. The lobster 

 is not capable of retaining the normal and necessary 

 concentration of salt in the blood. 



Experiments carried out with various mixtures of 

 fresh water and sea water showed that the animals be- 

 came very feeble when the salt concentration in the 

 water was low (from 25 per 1000 salt down to 20 per 

 1000). Under such conditions, the rate of metabolism 

 (oxygen consumption) increased about 50 per cent, 

 which entails, as will be seen later on, another technical 

 difficulty in connection with the storage of lobster. At 

 even lower salt concentrations (from 20 per 1000 and 

 downwards), the lobster could only remain alive for a 

 very short time 



The word " salt " as used in the foregoing should 

 be understood to be the mixture of mineral salts usually 

 present in sea water. This mixture contains apart from 

 ordinary salt (by technicians called sodium chloride, 

 ordinarily called kitchen salt or just common salt ) , also 

 numerous other kinds of salts, which are all more or 

 less vital to the growth of the lobster. Many of these 

 salts only appear in very small quantities in sea water. 



The mixture of artificial sea water which was used 

 in these experiments contains five of the most important 

 components of natural sea water approximately in 

 the same concentration as in sea water. There 



