21. A prosecution under this Act against a licensed person shall not be instituted except with the assent in writing of the Secretary of State. 22. This Act shall not apply to invertebrate animals. II.--ANÆSTHETICS UNDER THE ACT In almost every case, the anæsthetic used is chloroform or ether; sometimes it is combined with or followed by morphia or chloral. The nature of the anæsthetic used in each case must, of course, be stated in the returns sent to the Home Office. Of the use of ether, it need only be said that animals take it well, and that there is no difficulty in rendering them unconscious with it. With some animals, chloroform is equally good. Professor Hobday, of the Royal Veterinary College, published in 1898 an account of 500 administrations of chloroform to dogs, for operations, with only one death. Still, for dogs and cats, ether is used in preference to chloroform. Other animals take chloroform well. Morphia is seldom used alone; but, in some cases, it is used after chloroform or ether. That morphia is a "real anæsthetic" is certain, for there are deaths every year from an over-dose of it. Again, it is certain that an animal, so far under the influence of morphia that it lies still, cannot be suffering, for the drug does not act directly on the muscles but on the higher nervous centres. Very rarely a dog may fail to come readily under the influence of morphia, may be excited by it, not narcotized. But this is altogether exceptional. An animal in such a condition would not be suited for experiment, and another anæsthetic would be given. Except in these rare cases, animals take morphia well and are profoundly influenced by it. Curare is not an anæsthetic under the Act. It is illegal to use it as an anæsthetic. In this country it is seldom used at all, and it is never used alone in any experiment involving any sort or kind of painful operation. In every such case a recognised anæsthetic must be given, and is given.[43] [43] See Part IV., "Curare." A good account of curare was published in the _Edinburgh Review_, July 1899.