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APPENDIX No. II. 



OBSERVATIONS ON THE SALMON DISEASE, 



EX 



I. M. C. Cooke, Esq., M.A., LL.D. 

 II. C. L. Jackson, Esq. 



III. Henry Lee, Esq., F.L.S. 



IV. Professor George Eolleston, M.D., F.R.S. 

 V. Erasmus Wilson, Esq. 



I. — Observations by Dr. M. C. Cooke. 



What is the Salmon Disease ? — However absurd it may seem to start with a DR. M. C. 

 question to which an answer might readily be given, on the faith of a lamentable COOKE, 

 experience, by a host of individuals, yet it is always advisable to proceed in "~ - " 



matters of this kind from some recognized basis, and to make sure of some 

 common ground as a starting point. This disease may be described as con- 

 sisting of morbid discoid patches, which first manifest themselves on the naked 

 parts of the fish body, as the head, tail, and fins, afterwards spreading to 

 other portions covered with scales. These patches are recognized at once by 

 the whitish filaments of a fungus which grows profusely upon the patches, and 

 which is known in science as Saprolegnia ferax. The external evidence of the 

 disease is the fungus seen growing on the morbid spots. From this disease 

 the fish evidently suffer considerable pain, and ultimately they succumb and 

 die. Thus far all seem to be agreed, that the disease manifests itself externally 

 by certain morbid spots on which a fungus flourishes. There also seems to be 

 an equal agreement in the results of examinations of the internal anatomy of 

 diseased fish that, apart from the spots, there is no evidence of the presence of 

 fungi in the viscera, heart, and other internal organs. In fact, that the whole 

 action of the fungus is confined to the external surface. This is an important 

 point, and one about which there should be no mistake. Is there, or is there 

 not, any evidence of the existence of fungoid spores or threads, or of fungus 

 action in fish previous to the external manifestations, or in the earliest stages 

 of the appearance of fungus on the surface ? Hitherto I have heard of no 

 instance in which the fungus has been found internally, up to an advanced 

 stage of the external manifestations. The conclusion to be drawn from this is, 

 that the fungus is not developed from within outwards, but establishes itself 

 on the surface, and works its way inwards. There is by no means a unity of 

 opinion whether the fungus is the cause or a consequence of the disease. We 

 recognize the diseased spots with the fungus growing upon them. They seem 

 to be indissoluble. Let us, however, attempt to consider them apart. 



The Fungus. — This has been so often and so fully described that it is 

 unnecessary to enter upon a long and elaborate description. Seen in the 

 water it consists of a dense mass of slender whitish threads, which are attached 

 by their base to the diseased spots, and radiate with their free ends in all 

 directions. The base consists of a creeping network of similar threads, which 

 are constantly growing and extending into the tissues, like as the roots of a 

 plant grow and extend themselves in the soil. These basal threads or root- 

 like filaments are called the mycelium. In the mushroom just such threads are 



