Oysters and Disease; An Account of Certain Observations Upon the Normal and Pathological Histology and Bacteriology of the Oyster and Other

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...again show a marked excess in the proportion of 2.1 to 1. The copper and iron in the white specimens are about normal, but the increased quantity of iron in the green is marked, being 2.5 times that of the former. Still there is relatively a large excess of copper as compared with iron in the green oysters, as is evident from the analyses, the ratio being 1.1: 1 for the white, and 1.8: 1 for the green. It is to be concluded, therefore, that the green colour of these diseased American oysters is coincident with the distribution of the excessive quantity of copper present, and that the copper is in consequence to be regarded as the cause of the colour. The histo-chemical investigations given further on confirm this conclusion. Manganese was also found by Dr. Kohn to be present in several of the kinds of oysters analyzed. Its detection is readily effected in the electrolytic method of analysis, as it separates at the anode as peroxide. Colne oysters contain 0.14 mgrme. per oyster, a quantity rather smaller than the amount of iron present. We must now turn to Dr. D. Carazzi's recent papers, in which he tries to show that the green colouration in oysters is in all cases a healthy condition, caused by the absorption of iron as a nutrient material from the surrounding medium by means of the surface epithelial cells, such as those of the branchiae and palps. A good deal that is stated by Carazzi is quite correct, but these are points which were known before. The novel statements are, we believe, entirely erroneous, and are the results either of mistaken observations, or inferences from observations. He rightly states that the Marennes green oysters may retain their colour for weeks or even months when taken to other waters in which greening does not take place. It ...