Summary.The bovine hypophysis serves as an excellent model for studying salient

A series of 25 adult male rabbits had multiple clip electrodes implanted in their diaphragms at open operation. Following postoperative recovery, the wires from these electrodes were connected to an electromyograph and records were made along with spirometry under normal physiological conditions. The spirometric tracings show four, rather than two, distinct respiratory phases. Just prior to the inspiratory and expiratory phases, a brief but appreciable phase exists during which no air moves into or out of the lungs. These static phases are called pre-inspiratory and pre-expiratory. Diaphragmatic activity continues throughout the respiratory cycle and surveys of the individual recordings reveal beyond question that, although there are many minor variations in degrees of activity between various muscular slips of the same rabbit's diaphragm (even adjacent slips), no obvious general pattern of difference exists. There is no electromyographic peculiarity of behavior in either the lumbar, costal, and sternal parts or for the right and left sides of the rabbit's diaphragm.

A smies of 15 rabbits had multiple intercostal clip electrodes implanted in the diaphragm and quadratus lumborum at open operation.Leads from the electrodes were passed to the back of the animals and soldered to a junction band. Simultaneous recordings of electromyographic activity and spirometry were made following recovery.The study revealed that the quadratus lumborum, acting simultaneously with the diaphragm, is an effective inspiratory muscle stabilizing the twelfth rib, converting i t into a fixed point from which the diaphragm acts. Very possibly the action of the quadratus pulls down the lower rib helping to increase the costo-diaphragmatic recess. Like the sternal, crural and costal portions of the diaphragm, the quadratus exerts a braking action to oypose the normal elastic recoil of the lungs during expiration.

No abstract

This study describes the hypophyseal angioarchitecture found in 79 adult New Zealand white rabbits. The pituitary glands and attached hypothalami were removed and carefully processed following routine histological methods, and the vascular organization was studied by light microscopy. Whole mounts of the pituitary median eminence complex were prepared and studied with a binocular dissecting microscope employing transmitted and epi-illumination. Arterial blood was found to be directed primarily to the neurohypophysis by the superior hypophyseal artery (SHA) and the inferior hypophyseal artery (IHA). A direct arterial blood supply was found to the adenohypophysis, but was limited solely to the pars intermedia by branches of the anterior hypophyseal artery (AHA) and the IHA. Capillaries of the pars intermedia were subdivided into an intermediate and a superficial plexus. The superficial plexus was situated between the intermediate plexus and the capillaries of the infundibular process. Capillaries of the superficial plexus did not form anastomoses between themselves, but ramified into the intermediate plexus to form a dense network of anastomosing capillaries that were continuous with capillaries of the pars distalis. A direct arterial blood supply was found only to the superficial plexus.