of Running Water on Skeletons. 437 



average ; the small volume of water at work would thus be to 

 some extent compensated. 



III. The foregoing notes present the chief points of interest 

 in connection with the subject in question. Two further remarks 

 appear appropriate with regard to the bones themselves. 



In the first place, the bones shew that the shoulder-joint of 

 the pony " A" was in an advanced stage of the disease called 

 Osteo-arthritis. Such an advanced stage of this condition is rare, 

 though not unknown, in the horse. The subject derives a special 

 interest from the point of view of the relation of disease to diet, 

 whether in Man or the horse. A purely vegetable diet would not 

 seem to be an efficient safeguard against the onset of Osteo- 

 arthritis. This subject has been ably discussed by Dr Balfour 

 in the Edinburgh Medical Journal (Feb. 1870, p. 713), where 

 special reference to Osteo-arthritis in the horse is made. Again, 

 Virchow (loc. cit. Z. fur Ethnologie) describes a not dissimilar 

 condition in bones of the extinct cave-bear (Ursus spelaeus) under 

 the name of Hohlen-gicht. Evidence of similar conditions in 

 early Tertiary ungulates was given by Professor Marsh at the 

 International Congress of Zoologists at Leyden in 1895. Secondly 

 and lastly, the water of this particular stream and marsh seems 

 to have contained sufficient acid (whether vegetable or other) to 

 lead to disintegration of the bones in certain places. This effect 

 must be very carefully distinguished from those of Osteo-arthritis. 

 In the latter, the joint-surfaces and the neighbouring parts 

 of the bones will be affected, and in such a way that erosion and 

 eburnation (polishing) of the joint-surface is found accompanied 

 by bony outgrowths around the margins of the latter. Erosion 

 due to acidity of the water first affects the very thinnest parts 

 of the bones and is accompanied of course by nothing in the way 

 of exostosis. The scapula of "A" shews both conditions very 

 excellently, the joint region affording evidence of Osteo-arthritis 

 as already said, and the blade of the scapula being perforated 

 in' its thinnest part by the solvent action of the water. 



31—2 



