VOL. XLVZII.3 PHILOSOPHICAL TRANSACTIONS. 565 



to these, have their seminal matter in them ; inasmuch as at this time these 

 vessels are more easily distinguished from the ureters, which convey the urine 

 from the kidneys into the bladder, and are situated near the seminal vessels on 

 each side of the spine. These may, without sufficient attention, be taken for 

 the ovaries ; and the more so, when these last are empty. When fishes have 

 spawned a few weeks, they are fit for the operation ; for, like hens, they have 

 small eggs in their ovaries as soon as they have laid their former clutch of eggs. 



When a fish is intended to be castrated, it must be held in a wet cloth, with 

 its belly upwards ; then with a sharp pen-knife, with its point bent backwards, 

 or other well-adapted instrument, the operator cuts through the integuments 

 of the rim of the belly, and in doing this he carefully avoids wounding any of 

 the intestines. As soon as a small aperture is made, he carefully inserts a hooked 

 pen-knife, and with this he dilates this aperture from between the two fore-fins, 

 almost to the anus. From the back of this instrument, being blunt, the danger 

 of wounding the intestines is avoided. He then, with two small blunt silver 

 hooks, of 5 or () inches long, by the help of an assistant, holds open the belly of 

 the fish ; and, with a spoon or spatula, removes carefully the intestines from one 

 side. When these are removed, you see the ureter, a small vessel, nearly in 

 the direction of the spine ; and at the same time the ovary, a larger vessel, lying 

 before it, that is, nearer the integuments of the belly. This last vessel you take 

 up with a hook of the same kind with those before mentioned, and detaching it 

 from the side far enough for the purpose, divide * it transversely with a pair of 

 sharp scissars ; remembering always, that great care is taken in not wounding, 

 or otherwise injuring, the intestines. After one of the ovaries has been divided, 

 proceed in the like manner to divide the other ; and then sew up the divided in- 

 teguments of the belly with silk, inserting the stitches at a very small distance 

 one from the other. 



Mr. Tull first put this method into practice, in order to prevent the excessive 

 increase of fish in some of his ponds, where the numbers did not permit any of 

 them to grow to an advantageous size. But from castration the increase was not 

 only prevented, but the castrated fish, as Mr. Tull asserts, grew much larger 

 than their usual size, were more fat, and, which is no trifling consideration, 

 were always in season. 



He observes further, that the spawning time is very various : that trouts, for 

 instance, are full about Christmas , perch in February ; pikes in March ; and 

 carp and tench in May. You must always, however, make some allowance for 

 climate and situation, with regard to the spawning of fish. And, from a very 



* Mr. Tull has frequently, to prevent the re-union of the divided cvaries, by which the eflect of 

 the oiieration might be defeated, taken out part of them, and yet the fish have survived. — Orig. 



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