416 LAND ANIMALS 



8 kg. and more. Snails, as has long been known, are especially abundant 

 both in species and individuals on limestone soils. Thus, of the 91 

 species of land gastropods about Basel, 81 occur on Jurassic terrain, 

 33 on Tertiary and diluvial soils, 60 on the Muschelkalk, and only 35 

 on igneous rock. 136 So, too, in the Solomon Islands, the land snails are 

 more numerous in the limestone areas than in those of volcanic sub- 

 soil. 137 There has been much discussion as to whether the success of 

 gastropods on limestone soil is directly related to the presence of lime. 

 It has been suggested that the cause of this phenomenon lies rather 

 in the number of fissures and recesses in limestone, in contrast to their 

 paucity in igneous rock, and the greater heat capacity of the limestone 

 soil. Undoubtedly, these are also of significance. It is important to note 

 that slugs are not less common on igneous rock than on limestone. It is 

 certain that calcareous soil is more favorable for the building of the 

 shell. If the weight of the empty shell of Arianta {Helix) arbustorum 

 is compared with the total weight of the animal, it is seen that the 

 shell is but 15-25% of the total weight on soils poor in lime, whereas 

 it is above 35% on soils rich in lime. However, the total weight shows 

 no dependence on the lime content. 



Lime is beneficial to many mammals. The roe deer bears stronger 

 horns in regions on lime-containing subsoil, other things being equal. 

 The body weight is also greatest on lime soil. In order to avoid sources 

 of error, it is necessary to compare roe deer from the same climate, so 

 that other factors such as those which are involved in the Bergmann 

 rule do not enter into consideration. 138 Cattle suffer at times from 

 brittleness of the bones in regions of igneous rock, as in the Black 

 Forest and in Norway, because the food does not provide the neces- 

 sary calcium for the development of the skeleton. On the other hand, 

 the Kentucky blue grass pastures which overlie limestone are famous 

 for their fine horses and cattle. Comprehensive investigations have 

 been made for man which show that in places where drinking water 

 has a high calcium content the number of sound teeth is greater 

 (compare table) the alkalinity of the saliva more pronounced, the 

 proportional number of men fit for military duty much greater. 139 



Lack of calcium in the drinking water seems to favor the appearance 

 of rickets; further, workers in limestone and gypsum quarries escape 

 tuberculosis to a striking degree. 140 Smaller herbivorous mammals 

 are more readily able to secure the necessary amount of calcium since 

 the quantity of food consumed is relatively greater and the weight of 

 the skeleton relatively less than that of the larger animals. To the 

 carnivores, the calcium supply of the ground is as truly important, 

 even though they secure their calcium from their prey. 



