SELECTIVE PARTIAL ABLATION OF THE FRONTAL CORTEX

ments were carried out. Huggins, Massina, Eichelberger and Wharton (1939) devised an isolation operation in the dog, which made possible the quantitative COllection of prostatic fiuid and the examination of its biochemical characteristics. Batelli (1921) described a method of obtaining semen from the guinea-pig by means of electrical stimulation, and thii method was subsequently employed by Moore and Gallagher (1930). Gunn (1936) developed a modification of Batelli's method of semen collection, which he applied to sheep in fertility studies, and which has been widely used for the purpose of artificial insemination in this animal. From the experimental viewpoint the direct examination of semen has obvious limitations, as it is a mixture of the secretions of various glands. During an investigation into the functions of the accessory sex glands of the common phalanger or possum (Trichosurus vUlpecula) , the necessity for obtaining the secretions of these glands and of the prostate gland in particular led to a trial of Batelli's method. The modifi· cation as introduced by Gunn was found to be the more suitable for the experimental production of an ejaculate and for the collection of the individual secretions of the accessory sex glands as will be described. The technique, as applied to the phalanger, is as follows: The animals are lightly anresthetized by ether and an electrode consisting of a hypodermic needle is inserted into the musculus sacrospinalis just below the last rib. The second electrode, a brass rod, insulated in such a way as to leave one centimetre of its tip conductive, is inserted into the rectum for a distance of three or four centimetres. Hy means of a transformer, the voltage is stepped down from 240 volts, alternating current, and 50 cycles per second, to 30 volts, alternating current, and 50 cycles per second. Three stimuli, each of ten seconds duration, are applied to the animal at intervals of one minute. Each stimulus . throws the animal into a generalized tonic seizure and opisthotonos. A profuse secretion from the paracloacal glands occurs (Bolliger and Whitten, 1948). The penis becomes semi-erect, and when the stimulus is terminated the animal relaxes and seminal fiuid is emitted. After three stimuli no further emission of seminal fiuid is usually obtainable. The seminal tluids are uncontaminated by urine and able to be collected independently of the paracloacal secretions. The procedure does not appear to have any harmful effects on the animal, which rapidly recovers, and it can be stimulated repeatedly at intervals of three or four days with no obvious harmful sequelre. Volumes up to 31 milli· litres of semen have been collected from one animal after the application of the three stimuli as described, but a more usual volume is in the vicinity of five to ten mill! litres. It would appear that there is a seasonal variation of the volume of the ejaculate in this animal, during winter months the whole of the accessory sex gland activity being at its lowest level. The fiuid collected has shown a variable tendency to rapid clotting. The ejaculate contains many motile spermatozoa, and sperm counts of up to 136,000,000 per millilitre have been observed. Spermatozoa can be excluded from the ejaculate by means of a soft bowel clamp placed across the neck of the prepenile section of ·the scrotum. Cowper's glands have been successfully surgically extirpated and pure prostatic secretion has been collected at will and in volumes of 10 to 30 millilitres at a time. A complete prostatectomy has been performed, the technique of which will be described elsewhere (Howarth, 1949). Thus the secretions of Cowper's glands or of the prostate gland can be obtained independently and with or without mixture with spermatozoa. Since seminal vesicles are absent in Trichosurus »ulpecula, the whole of the accessory sex gland secretiori can be fractionated by the methods described. The prostatic fluid obtained from Tricnosuru.s vulpecula, the characteristics of the spermatozoa, and the secretion of the Cowper's glands are being investigated.