Five healthy cattle were injected intravenously both thiopental sodium and chloral hydrate as a combined anesthesia. Each of the cattle were used twice in this experiments. And then, from which the following results were obtained.
1) Thiopental sodium that were the first anesthetic were administered them a dose of 10 mg/kg of body weight.
In four cases of ten, surgical anesthesia stage (III₃) was maintained for 5-10 minutes. Fifteen minutes later, then chloral hydrate were administered them (An average volume was 71.4mg/kg.), until surgical anesthesia stage (III₃) was obtained. Consequently, surgical anesthesia was obtained for 10-20 minutes in eight cases of ten.
2) During the combined anesthesia, body temperature of all the subjects fell slowly and pulse rate usually increased. Five minutes after the administration of chloral hydrate, pulse rate reached a value 2.3 times higher than the preanesthesia.
Respiratory rate generally increased but both tidal volume and minute volume decreased.
3) The mean values of blood gases and acid-base balance in arterial blood showed the largest changes ten minutes after the administration of chloral hydrate ; pH was 0.088 lower, PCO₂ was 30% higher, PO₂ was 33.7% lower and O₂ saturation decreased 10% than the preanesthesia. Plasma bicarbonate hardly changed during the combined anesthesia.
Therefore, in view of these facts, it appeared that respiratory acidosis was occured within the scope of the compensation.
4) The erythrocyte, hemoglobin content and the hematocrit, Na⁺, K⁺ and Cl_- in the plasma electrolyte did not show much changes. The value of the blood sugar clearly increased 37% higher than preanesthesia.

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In the present paper, the possibility of clinical use of Xylazine in the anesthesia of dog and cat was discussed based upon experiments with overdose of Xylazine and upon clinical use of Xylazine-Ketamine hydrochloride combination and of Xylazine-Pentobarbital sodium combination in dogs and cats.
Administration of 9 mg/kg (about three times of usually recommended dose as anesthetics) of Xylazine through various routes was proved at least not to be fatal as far as clinical manifestations are concerned, as all animals could tolerate this dosage without any serious troubles.
Since, even with quite high dosage of Xylazine as high as 9 mg/kg, deep anesthesia could not be obtained, Xylazine was used in combination with Ketamine hydrochloride and with Pentobarbital sodium. In both these combinations, more satisfactory anesthesia was obtained, not only with extensively low dosage of Ketamine hydrochloride or of Pentobarbital sodium, but with less undesirable reactions, characteristic in these two anesthetic agents.
Being specific with these combined anesthesia, was that the effective post-anesthetic sedation was retained for rather long period, even after fairly rapid disappearance of anesthetic effects.

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