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atheromatous plaques and are surrounded by chronicinflammatory changes. In a series of cases examined,Nelson found that haemorrhage from these sinusoidswas not uncommon. Such haemorrhages in the deeperzones of the intima healed by granulation tissue inwhich new capillaries were numerous. An increase offibrosis evidently then followed and predisposed thepatient to a further haemorrhage, a vicious circle thenbeing set up. The condition was present in 11 out of 17instances investigated, and in 9 thrombotic occlusion ofthe lumen was also present. The factors determiningthe intimal haemorrhage are probably weakening of thesinusoidal wall by toxic action and transient raisediatraluminar pressure induced by exertion or emotion.

WAR INJURIES OF THE LUNGS

IT is wise to remember, as Sir Joseph Barcroft pointedout in opening the discussion on lung injuries at Portonreported in our columns last week (p. 197), that while theaerial offensive on England has not as yet included gasattacks, not only H.E. but gas bombs may be used infuture raids. Both can cause lung injuries, and thediscussion concerned itself with the clinical differentiationof the two types of pulmonary damage. Those whotook part agreed that histologically the differentiationis relatively straightforward. Gases which act on thelungs cause bronchial spasm, destroy the bronchialmucous membrane, damage the alveolar walls, and pro-duce acute pulmonary cedema. Pulmonary damagewhich occurs as a result of H.E. explosions takes the formof heemorrhagic lesions, which may be associated withsigns of pulmonary fat-embolism, and occasionally withthose of carbon-monoxide poisoning. It is to be hopedthat future events-if they materialise-will justify theoptimism of the participants in the discussion, and thatit will be as simple to make a differential clinical diagnosisof nonfatal forms of lung damage as it is to differentiatethem histologically in the dead. At present it is un-doubtedly true that not enough is generally known aboutthe pulmonary changes which occur in H.E. incidentsto distinguish the factors which may be responsiblefor different types of lung damage. However obviousit may sound, Professor Ryle’s suggestion that the differ-entiation of pulmonary injuries would be assisted by theknowledge of the history of the incidents responsiblefor them should be firmly borne in mind, to help indistinguishing not only gas injury from H.E. injury butalso one form of H.E. injury from another. The lackof such histories may well make the problem of a com-bination of gas and H.E. injury in the same casualtiesnot just " more complex " as Prof. Shaw Dunn remarked,but completely insoluble.

THE AUTONOMIC NERVOUS SYSTEM

THE sympathetic chain was so called because of itsnumerous connexions with other nerves. It was

supposed to be the major factor irP mediating " sym-pathies," or reactions accompanying but bearing nodirect relation to the main reaction ; an example beingthe pupillary constriction in a blind eye accompanyingthe constriction in the illuminated seeing eye." Sympathetic " has now become a purely anatomicalterm, applied to the autonomic outflow from the thoracicand lumbar segments. The term parasympathetic,also anatomical, refers to the cranial and sacral outflowswhich overlap the sympathetic peripherally, actingl

usually in the opposite sense. One of the outstandingdiscoveries of the last twenty years has been thatautonomic postganglionic fibres can be classified on

a physiological basis into those which act by liberatingacetylcholine (cholinergic) and those which liberate anadrenaline-like substance (adrenergic) at the effector

organ. The partition between cholinergic and adrener-gic corresponds roughly, but not exactly, to theparasym-

pathetic and sympathetic systems respectively. In ahistorical survey and a later review of modern work onthe autonomic, Sheehan points out that, concurrentlywith these studies of humoral transmission of impulses,there has been a growing realisation that the autonomicis not a system on its own; it has not only intimateassociations with the spinal cord, of which it is an

outgrowth, but important connexions with highercentres, to which it is subordinate. Interest at presentcentres chiefly in the hypothalamus, but there isno doubt that the cerebrum, especially the precentralcortex, also influences the autonomic. The activity ofany group of cells in the central nervous system dependson the intensity of its " excitatory state." Such a

group might have either a predominantly visceral or apredominantly somatic function : yet its final activitymight be determined-perhaps raised above a significantthreshold-by a quite subsidiary access of excitationfrom the complementary source. This seems furtherevidence that the autonomic and somatic nervous

systems are inseparable.

ANATOMY OF INGUINAL HERNIA

DESCRIPTIONS of the surgical anatomy of the inguinalregion usually assume that the arrangements of thestructures met with at operation for hernia is the sameas is found in dissection of the normal, non-herniatedsubject. Ashley and Anson 2 have made careful dissec-tions to decide how far this is true. They found thatindirect passage of a fairly large hernia did not take place-the peritoneal sac passed through the wall directly, inits course displacing the inferior epigastric arteryinwards, so that the first part of the artery passed almosthorizontally, and then turned ata right angle to passupwards behind the rectus abdominis muscle. Hessel-bach’s triangle did not exist. The inferior epigastricvessels were thus important medial and inferior relationsof the neck of the sac. The sac had a more medial

disposition than is conventionally described, and on thefloor of the abdominal ostium was formed by the iliacvessels, the anomalous obturator (present in this case),the ductus deferens and the internal spermatic vessels.Their other main observation was concerned with theidentity of the various coverings of the hernial sac.

These are usually described as the external spermaticfascia, derived from the external oblique ; the cremas-teric fascia and muscle, derived from the internaloblique ; and the internal spermatic fascia, derived fromthe transversalis muscle. By dissection the coveringswere identified and separated in the scrotum and tracedupwards to the parietal layers of the abdominal wall.It was found that they could be definitely followed totheir source. In all cases examined the contributionfrom the external oblique was entirely fascial, consistingof the conjoined fascia which invests the two aspectsof the muscle. In the cremasteric layer scattered musclefibres were identifiable, but there were no definiteaponeurotic fibres, and it was concluded that this layerwas predominately fascial. The internal spermaticcovering represented a fusion of the thin outer laminaof the fascia investing the transversalis and ileopsoasmuscles and the thicker inner one, commonly known asthe transversalis fascia.

Mr. E. Rock Carling, senior surgeon to the West-minster Hospital, and Dr. S. P. Bedson, F.R.S., pro-fessor of bacteriology in the University of London atthe London Hospital, have been appointed members ofthe Medical Research Council, in succession to Prof.G. E. Gask and Dr. W. W. C. Topley, F.R.S., who retireon Sept. 30.

1. Sheehan, D. Arch. Neurol. Psychiat. 1936, 35, 1081; Ann Rev.Physiol. 1941, 3 (reviewed on page 218).

2. Ashley, F. L. and Anson, B. J. Quart. Bull. Nthwest Univ. 1941,15, 114.