Marjorie M. L. Prichard

Studies of the Carotid Rete and Its Associated Arteries

This work records an investigation of the anatomy of the cranial blood supply in various species of mammal. The findings were based on a study of radiographs of specimens injected with a radioopaque mass and of casts of the vessels made by injection of neoprene latex, and on dissections of injected preparations. A well-developed carotid rete was found to be present in the cat, sheep, goat, ox and pig, and a rudimentary form of this structure was found in the dog. In the cat the rete is situated extracranially, but in the other species it lies within the cranium in the cavernous sinus. There is no carotid rete in the rabbit or the rat. The carotid rete consists of a compact network of intertwined, freely anastomosing arteries, and is related to the branches of the trigeminal nerve. When the rete is situated intracranially there is a variable degree of communication across the mid-line with the rete of the opposite side. W hether situated intracranially or extracranially the rete lies within a venous lake. The presence of a well-developed carotid rete was associated with the non-persistence of, or a degenerating internal carotid artery. A thin fibrous cord was the only rem nant of this artery found in the cat. In the goat, sheep and pig the internal carotid artery was absent proximal to the rete, but the large trunk which connected the rete with the circle of Willis was identified as representing the still persisting distal segment of this artery. In the ox (a young animal) a similar trunk connecting the rete with the circle of Willis formed the continuation of a still persisting but relatively narrow proximal segment of the internal carotid artery. The main vessels which may supply the carotid rete are the internal maxillary artery (usually via the ramus anastomoticus and the arteria anastomotica), the ascending pharyngeal artery, and the occipital artery. In the cat, sheep, goat and ox the chief vessel of supply is the internal maxillary artery, but in the pig it is the ascending pharyngeal artery. In the ox a substantial contribution is provided by the occipital artery. Both the ramus anastomoticus and the arteria anastomotica form connexions between the external and internal carotid systems and they join one another within the cavernous sinus. It is at his site that the intracranial carotid rete is developed, but the extracranial carotid rete, seen in the cat, is situated around the internal maxillary artery at the site of origin of the arteria anastomotica of the artiodactyls. The variations in the situation of the carotid rete in different species is along the line of the arteria anastomotica. It is suggested that the arteria anastomotica and the ramus anastomoticus respectively are homologous with the recurrent meningeal and the middle meningeal arteries of the rabbit and man. The arteries which supply the orbital and the ethmoidal regions are described and the homologies of the external ophthalmic artery are discussed. The great variability in the supply of these territories which was seen in the cat is thought to be associated with the presence of an extracranial carotid rete. In spite of variations in different species of animal a basic pattern can be discerned in the major arteries supplying the head. It is suggested that this basic pattern is related to a primitive stapedial artery, and that the variations seen are due to modifications of the branches of this earlier vessel. The circle of Willis was found to derive its blood supply from one or more of five sources: the internal carotid artery, the external carotid arterial system, the ascending pharyngeal artery, the vertebral artery (via the basilar artery) and the occipital artery. In the absence of an internal carotid artery the greatest contribution of blood passes to the circle of Willis through the carotid rete. An occipito-vertebral anastomosis seems to be of some importance in supplying the circle of Willis in the cat, pig, dog and rabbit. In the sheep, goat and ox the direction of the flow of blood in the basilar artery would appear to be away from and not towards the circle of Willis. In the pig the two anterior cerebral arteries anastomose in the mid-line and continue forward as a single vessel. The peculiar structure of the vessels which compose the carotid rete suggests that this compact network has a haemodynamic significance, and since the rete lies in the pathway of the major artery or arteries which supply the brain, its existence and possible influence should be borne in mind when problems of the cerebral circulation are considered in species in which this structure is present.

Transection of the pituitary stalk in man: anatomical changes in the pituitary glands of 21 patients

In recent years hypophysectomy (Luft and Olivecrona, 1953) and adrenalectomy (which is nearly always combined with ovariectomy) have been used as methods of treating cases of advanced cancer of the breast (Atkins, Falconer, Hayward, MacLean, and Schurr, 1966) and the results of comparative trials suggest that hypophysectomy is slightly the more effective of these two operations (Atkins, Falconer, Hayward, MacLean, Schurr, and Armitage, 1960). As an alternative to hypophysectomy neurosurgeons have sometimes used the operation of pituitary stalk section for relieving such cases and also for treating patients with cancer of the prostate (see Schurr, 1966). In addition pituitary stalk section has been used for patients with advancing diabetic retinopathy (Field, Schepens, Sweet, and Appels, 1962; Cullen, Harris, Munro, and Duncan, 1965; Fager, Rees, and Bradley, 1966). In assessing the merits of this particular operation as a means of depressing pituitary function, it is important to know the extent to which the structure of the gland is altered and its functions impaired. There are few reports in the literature on the effects of stalk section on the human pituitary (Dandy and Goetsch, 1911; Russell, 1956; Daniel, Prichard, and Schurr, 1958; Le Beau and Foncin, 1960; Nicolaidis, 1962; Adams, Daniel, Prichard, and Schurr, 1963), although much information has now been obtained on the effects of the operation on several species of animal (Harris, 1950; Barrnett and Greep, 1951; Greep and Barrnett, 1951; Benoit and Assenmacher, 1953; Campbell and Harris, 1957; Daniel and Prichard, 1958; Holmes, 1961, 1962; Laszlo, David, and Kovics, 1962; Adams, Daniel, and Prichard, 1963a, b, c; 1964a, b, c; 1966a, b; Jacobsohn, 1966). We have now had the opportunity of examining the glands of 21 human patients surviving for various periods of time after stalk section and in this paper we report our findings in these pituitary glands. MATERIAL AND METHODS

Some Effects of Transection of the Pituitary Stalk

As we look at this whole field, the most challenging, and the least conquered and understood, is that set of phenomena which we associate with the mind. Here is the great challenge to the physician and to the scientist. To the physician because it is particularly in this respect that one individual differs from another, and because the meeting and mutual understanding of minds constitute the essence of the doctor-patient relationship ; to the scientist because here is presented an elementary problem of scientific method?namely, that of classifying the facts in such a way that allows numerical values to be assigned to them, and formulation of these in terms of a simple hypothesis. This challenge has been offered before to the scientific method, and