J. E. Markee

TWO-JOINT MUSCLES OF THE THIGH

Evidence from functional studies in the dog and morphological studies in the human suggests that all of the muscles of the human thigh can, by contraction, produce tension at one joint only. The evidence presented also indicates that movement at the hip without movement at the knee can be produced by a part of the rectus femoris, the sartorius, the gracilis, the semitendinosus, the semimembranosus, and the biceps femoris; and that movement at the knee without movement at the hip can be produced by the gracilis and the biceps femoris. Whereas most of the tension resulting in movement at two joints is transmitted by tendons to attachments to bone, most of the tension resulting in movement at a single joint is transmitted to fascia. Eccentric contraction of the parts of these muscles which act over two joints may facilitate coordinated, simultaneous movements at both the hip and the knee. The muscles which act over two joints are ideally arranged to participate in certain kinds of force couples. When the body weight is raised from a chair, some of the tension produced by the quadriceps femoris can be used by the hamstrings to extend the hip joint, even when the hamstrings are not shortening. Prevention of excessive gliding at the knee joint appears to be one function of two joint muscles.

Spontaneous ovulation in the rabbit following combined estrogen-progesterone treatment.

Summary Following treatment with estrogen and progesterone 4/10 rabbits ovulated spontaneously, i.e., without the coital stimulus normally required to induce LH release from the hypophysis in this species.

A Quantitative Study of the Vascular Beds of the Hand

This study deals with certain quantitative relationships of the human hand—namely, the percentage of the volume constituted by such of its components as dermis (22 per cent), muscle (15 per cent), tendons (10 per cent), bone (37 per cent), and connective tissue (15 per cent) and the amount of the vascular bed located in those components. In three of the 100 hands utilized in this study the weight and indirectly the volume of a plastic cast of the vascular spaces was determined. The vascular space constituted about 11.8 per cent of the volume of the three normal hands. By dissecting the casts of the three hands, it was determined that the vascular bed was distributed as follows: within the connective tissue 47 per cent, within the bones 22 per cent, within the dermis 16 per cent, within the muscles 13 per cent, and within the tendons 2 per cent. The distribution of small, medium-sized, and large vessels within each of the tissues of the hand was determined by teasing the cast apart and weighing separately the fragments with diameters less than 134 micra, with diameters between 134 and 536 micra, and with diameters larger than 536 micra. In such tissues as the dermis, muscles, periosteum, or bone, 75 to 85 per cent of the vascular bed is made up of vessels with a diameter less than 135 micra; whereas in these same tissues vessels with a diameter greater than 536 micra make up 4, 10, 10, and 5 per cent, respectively, of the vascular bed. Tissues with a low metabolic rate are supplied by fewer small vessels and transmit a disproportionate number of large vessels; thus, in tissues such as the dorsal connective tissue, the nerves, and the tendons, the small vessels constitute only 51, 67, and 50 per cent of the vascular bed, whereas the vessels larger than 536 micra make up 38, 5, and 41 per cent, respectively, of the vascular bed.

Evidence taht Copper Acetate Induces Ovulation in the Rabbit by Direct Stimulation of the Adenohypophysis

Copper salts induce ovulation in the estrous rabbit, 1 2 a species which normally ovulates only after copulation. The natural mating stimulus, which results in the release of luteinizing hormone from the adenohypophysis, involves the hypothalamus and the pituitary stalk 3 and includes both adrenergic and cholinergic components. 4 Bischoff 5 suggested that copper activated the hypophysis by toxic stimulatory effects on the nervous system. The idea appeared to be confirmed by the results of Brooks, 3 who found that copper failed to induce ovulation in rabbits whose hypophyseal stalks had been severed, and Harris, 6 who reported that very weak dosages of copper acetate injected directly into the third ventricle stimulated the ovulatory response. We were led to doubt that copper-induced ovulation is purely a nerve-stimulation phenomenon when dibenamine and atropine, in dosages adequate to block the copulation stimulus from reaching the hypophysis, 4 , 7 failed to prevent copper acetate from activating the release of an ovulatory surge of LH. 8 It therefore seemed desirable to test the hypothesis that copper might exert its stimulatory action directly upon the anterior pituitary. Sexually mature female rabbits ranging in weight from 2.5 to 4.3 kg were employed; in this study. To insure an estrous condition, each animal was treated with 85 μg estradiol benzoate on 2 successive days prior to copper administration, for ovulation is not induced by copper in anestrous rabbits. 9 A control series of 10 females revealed that the estrogen alone would not stimulate LH release. The hypophysis was approached parapharyngeally as in earlier studies, 10 11 and 4 attempts were made at 5 or 10s minute intervals to inject a total of 0.15 ml of 0.1% copper acetate, buffered with 0.1% sodium acetate, 12 directly into the pars distalis.