724 REPORT— 1895. 



in water whicli is more or less contaminated by sewage, but it is still an open 

 question as to tbe resulting effect upon the oyster. 



4. To determine whether oysters not infected with a pathogenic organism, but 

 gi'own under insanitary conditions, have a deleterious effect when used as food by 

 animals. 



5. To determine the effect upon the oyster of infection with typhoid, both 

 naturally — i.e. by feeding with sewage water containing typhoid stools, and artifi- 

 cially — i.e. by feeding on a culture in broth of the typhoid organism. 



6. To determine the fate of the typhoid bacillus in the oyster — whether it is 

 confined to the alimentary canal, and whether it increases in any special part or 

 gives rise to any diseased conditions ; how long it remains in the alimentary canal ; 

 whether it remains and grows in the pallial cavity, on the surface of the mantle 

 and branchial folds; and whether it produces any altered condition of these parts 

 that can be recognised by the eye on opening the oyster. 



7. To determine whether an oyster can free its alimentary canal and pallial 

 cavity from the typhoid organism when placed in a stream of clean sea water; and, 

 if so, how long would be required, under average conditions^ to render infected 

 oysters practically harmless. 



B. The methods which we employed in attaining these objects were as 

 follows : — 



1. Observations upon oysters laid down in the sea, at Port Erin — 



(a) Sunk in 5 fathoms in the bay, in pure water. 



(b) Deposited in shore pool, but in clean water, 



(c) Laid down in three diH'erent spots in more or less close proximity to 



the main drain pipe, opening into the sea below low-water mark. 



These were to ascertain differences of fattening, condition, mortality, and 

 the acquisition of deleterious properties as the result of sewage con- 

 tamination. 



2. Observations upon oysters subjected to various abnormal conditions in the 

 laboratory. ' 



(a) A series of oysters placed in sea water and allowed to stagnate, in 

 order to determine effect of non-aeration. 



(b) Similar series in water kept periodically aerated. 



(c) A series placed in sea water to which a given quantity of fresh (tap) 



water was added daily, to determine effect of reduction of salinity. 



(d) A seiies of oysters weighed approximately, and fed upon the follow- 

 ing substances, viz. : — 



(1) Oatmeal. 



(2) Flour. 



(3) Sugar. 



(4) Broth. 



(5) Living Protophyta (Diatoms, Desmids, Algae). 



(6) Living Protozoa (Infusoria, &c.). 



(7) Earth. 



In this series of experiments the oysters were fed every morning and the 

 water aerated, but not changed (evaporation was compensated for 

 by the addition of a little tap water as required). The oysters were 

 weighed from time to time, and observations made upon the ap- 

 parently harmful or beneficial etl'ects of the above methods of 

 treatment. 



' The oysters were kept in basins in cool rooms of constant temperature, shaded 

 from the sun, both at the Port Erin Biolosrical Station and also in the Pathological 

 and Zoological Laboratories at University College, Liverpool. 



