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curve, but by testing the urine with ferric chloride. Thosewho still cling to the single-gene hypothesis of essentialhypertension can best prove their point by demonstratingthe biochemical fault of which it would be the manifesta-tion. Good luck to them.

Oxford. G. W. PICKERING.G. W. PICKERING.

LOGIC, HYPERTENSION, AND THE SNARK

THE BELLMAN.The Snark Club,

Cambridge.

SIR,-Sir Robert Platt may be right about hypertensionbut by (Sir) George (Pickering), he is wrong about theSnark! Whoever heard of Dodgson, C. L., as the authorof the Agony? And what would Lewis Carroll have saidof the expression " super-Snarkism " ? By implication, SirRobert attributes to the Snark the immortal phrase" WhatI tell you three times is true ". As my crew know onlytoo well after sailing together for 28 years, it was I whosaid this.

REDOX POTENTIAL IN ASSESSMENT OF

COLISTIN

STEVEN ZADOR.Department of Pathology,West London Hospital,

London, W.6.

SIR,-In redox-potential measurement for studying theeffect of antibiotics on microorganisms 1 a sensitiveelectronic device 2 is used with electrodes dipping into aculture-medium which has been inoculated with the

microorganisms to be studied, whilst the culture is beingincubated.

Several cultures may be charted simultaneously and,thus, the inhibiting effects of an antibiotic on a number oforganisms may be studied. Equally, the relative effectof antibiotics on any particular organism may be investi-gated by comparison of the adjacent charts.This method was used to study a recently introduced anti-

biotic colistin (’Colomycin’), a polypeptide with a penta-cyclic ring and a side-chain terminated by hepto-octanoic-acid ester. It is, therefore, somewhat similar to polymyxin B,but contains no phenylalanine in the molecule, and, as the

1. Zador, S. J. clin. Path. 1958, 11, 278.2. Zador, S. Proc. 2nd Int. Congr. med. Electr. Paris, 1959, p. 517.

methane sulphonate, it is without the unpleasant side-effectsometimes encountered with polymyxin.

In the examples illustrated here, the redox potentialsdeveloped in a seeded culture-medium have been measuredcontinuously for 10 hours. Growth-rates of Escherichia coli,Bacterium aerogenes, and Salmonella paratyphi B have been

separately studied after the addition of various antibiotics.In the case of Esch. coli, the control culture begins to showactivity after a latent period of 2 hours, and from then on isprogressive. In the presence of 10 {.Lg. per ml. of tetracycline(’Achromycin’) the inhibiting period is extended to 8 hours,after which activity is progressive. There is no evidence of

growth in the same concentration of colistin even after 10 hours.With B. aerogenes in the control and with tetracycline

present, growth is obvious after 2 hours, whereas, with

colistin, activity is not significant even after 8 hours.The curves with S. paratyphi again show growth in the

control after 2 hours, but no activity when either tetracyclineor colistin is present even after 61/2 hours. A test withthis organism, used in this particular experiment, suggeststhat chloramphenicol has little or no inhibiting effect on

proliferation.I wish to express my thanks to Pharmax Ltd. for making available

’ Colomycin’ to me. I also wish to express my gratitude to Dr.Reginald Milton and to Mr. H. Blunt for their assistance and advice.

This communication is part of work done under a grant from theDan Mason Research Foundation.

AN IMPROVEMENT TO THE CROSBY PERORALINTESTINAL BIOPSY CAPSULE

SIR,-Dr. Read and his colleagues (April 28) write thatdislodgement of the cap from the Crosby-Kugler intes-tinal biopsy capsule is one of the main disadvantages ofthis instrument. And they have gone to considerabletrouble to modify the instrument by redesigning the cap.We have had much experience with this instrument atthe Tropical Medical Research Laboratory in PuertoRico and have used it in over 400 intestinal biopsies. Atfirst several resident physicians did dislodge the cap

by too vigorous injection of saline or radio-opaquedye. But we have overcome this by merely windinga small piece of plain adhesive tape, 1/8 in. wide,over the top and sides of the instrument and byoverlapping this with another piece of adhesivewhich spans the girth of the instrument. Thesecond piece of tape should cover the junction of thebody and the cap.

This simple procedure has allowed us to perform over300 biopsies without loss of the cap, whereas during thefirst 100 biopsies we lost three.Some of your countrymen on a recent visit to our

laboratory encouraged us to write a note concerning thisinstrument. We have found that using no. 160 poly-ethylene tubing, instead of the larger size no. 200,shortens the time the capsule takes to reach the smallbowel. Presumably the lighter tubing lessens the dragon the capsule. The amount of suction exerted on the10 ml. syringe used to trigger the firing mechanism ofthe capsule is also important. As a rule the greater thesuction, the larger the biopsy. Good springs and asharpened blade are essential. A misfire, or failure of theknife blade to sever the mucosa completely, may resultfrom neglect of these safeguards.The inexperienced operator also may have difficulty

in retrieving the capsule once it is fired. During theremoval of the instrument it is not unusual for the

pylorus to contract as the capsule enters or nears thisportion of the bowel. The inexperienced often believethe instrument is stuck. Our resident physician some-

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times became concerned about this and wanted to abandonthe procedure. Usually, simple traction after a few minutes’rest, or asking the patient to extract the capsule, was all thatwas necessary to retrieve it. We use two methods to retrievethe capsule: (1) asking the patient to remove it, and (2) askinghim to kneel on his hands and knees, with his head extended,while the operator slowly withdraws the capsule. At timesa sharp pat on the back overcomes pyloric tension. Difficultyis also encountered occasionally at the cardia, but usually thisis readily overcome by persistent tension on the tubing of thecapsule.

Experience is the best guide in the use of this instrumentand generally converts the sceptic into an enthusiastic booster.The assembling of the instrument is also a matter of familiarisa-tion. Our nurses now assemble and pass the instrument, whilethe physician merely fires and removes, or supervises removalof the instrument.

THOMAS W. SHEEHY.

Medical Division,U.S. Army Tropical Research

Medical Laboratory,APO 851, New York.

SODIUM-RETAINING STEROIDS

IN NON-ŒDEMATOUS PATIENTS

H. J. GOLDSMITH.Renal Insufficiency Unit,Sefton General Hospital,

Liverpool.

SIR,-Dr. Mills (June 16) has made the interestingobservation that some patients with pyelonephritis butnormal blood-pressure and excretory function are unable,when treated with 9-alpha-fluorohydrocortisone, to

excrete a sodium load in a normal manner. He postulatesa disturbance of the juxtaglomerular apparatus (J.G.A.) asa result of recurrent urinary infections.

I should like to suggest a possible mechanism for such aJ.G.A. disturbance; Kincaid-Smith demonstrated histologi-cally intrarenal arterial obstruction in human acute and chronicpyelonephritis. Arterial narrowing is also a feature of the

kidney in scleroderma, in which disease it precedes the develop-ment of hypertension. In kidneys of patients with this disorderstudied by biopsy, hypertrophy, and hypergranulation of theJ.G.A. were observed. Its severity was proportionate to thedegree of arterial narrowing. These patients were not hyper-tensive or taking drugs.

It is possible that such vascular lesions in the three patientsdescribed by Dr. Mills are the cause of focal overactivity ofthe J.G.A. Excessive production of renin would ensue and inturn cause hyperaldosteronism.

INADVERTENT HYPOTHERMIA

WALTER ZINGG.Children’s Hospital,Winnipeg, Manitoba.

SIR,- Your annotation (April 28) draws attention to theapparent discrepancy between the possible beneficialeffects of induced hypothermia for certain conditions, andthe well-substantiated danger of unintentional andaccidental hypothermia in children, especially in newborns.This discrepancy is only apparent. The reports ofaccidental and unintentional hypothermia in all age-

groups point out that the danger period is not on admissionto hospital, but during rewarming. Unfortunately, ourknowledge regarding the best management of accidentalhypothermia is still very limited, and consequently thecourse of the patient during the rewarming period is oftenunsatisfactory.When induced hypothermia is employed in the operating-

room, the rewarming period is carefully supervised. It is wellknown that if the patient is not completely rewarmed, the tem-perature will drop again and complications very similar to thosedescribed in your annotation will ensue. The reasons for thisare not entirely clear. One might postulate that these patientshave an intact thermoregulatory mechanism, and therefore

1. Kincaid-Smith, P. Lancet, 1955, ii, 1263.

would try to increase their body temperature. This would beassociated with an increase in the total oxygen consumption andan increased load on the circulatory and other organs. In sick

patients, and postoperatively, this additional load may not betolerated.

Accordingly, I submit’that there is no real difference betweenthe effects of accidental hypothermia and induced hypothermiaat that stage. Careful rewarming is necessary in both cases.However, since induced hypothermia is of short duration, rapidrewarming seems advisable: similarly with accidental coolingduring major surgery. Hypothermia after prolonged exposureto cold, either in air or in water, is probably better treated withslow rewarming without the addition of external heat.

EFFECTS OF GIVING VASOPRESSORS TO

PATIENTS ON MONOAMINE-OXIDASE INHIBITORS

SIR,-The interesting reports of Dr. Mason (May 19)and Dr. Dally (June 9) on this syndrome seem to explaina bizarre incident sustained by a patient anaesthetisedby me on June 6. A short account may help otheranaesthetists faced with similar cases.A woman of 33 had lost three sisters from subarachnoid

haemorrhage due to rupture of aneurysms of the Circle ofWillis. This had worried her to the extent that it had been

thought fit to treat her with chlordiazepoxide (’ Librium’)and phenelzine (’Nardil’) for a month before admission.When she began to have headaches she was referred to Dr.John Walton who advised bilateral angiography, althoughthere was no evidence that she had had a subarachnoid

haemorrhage.Premedication was with pethidine 50 mg. and atropine

0-65 mg. Anaesthesia was induced with 300 mg. of sodium

thiopentone and 50 mg. of suxamethonium, and the tracheawas sprayed with 2 ml. of 4% lignocaine. Intubation with acuffed armoured endotracheal tube followed, and anaesthesiawas maintained with nitrous oxide, oxygen, and 1% halo-thane. Stable conditions prevailed for thirty-five minuteswhile stereo-lateral, anteroposterior, and oblique films of theright carotid tree were exposed.

Palpation of the left carotid artery before puncture causedthe blood-pressure to fall to 80 mm. Hg making the arterydifficult to feel. In order to facilitate puncture 10 mg. of

mephentermine was given intravenously via a Gordh needlein the dorsum of the foot. This was immediately followed bythe appearance of gross tachycardia, faster than 200 perminute, and a blood-pressure of 190 systolic. There was noalteration in respiration, the veins remained dilated, andthere was no sweating.

In the belief that this might have been an episode ofparoxysmal tachycardia, pressure was applied on the eyeballs,but did not influence the heart-rate. The halothane waswithdrawn and 100% oxygen administered. After seven or

eight minutes the rate suddenly slowed to 120 per minute, andcoupling appeared, followed by a rhythm largely regular butwith a few extrasystoles. About fifteen minutes after theadministration of the mephentermine the rate was once againregular at 80. The blood-pressure fell as the tachycardia sub-sided, and was normal twenty minutes after injection.

Simultaneously with the hypertension a hxmatoma of theright carotid sheath developed and in view of all the happeningsit was considered wise to abandon the angiography.The patient’s subsequent progress was uneventful and a

postoperative electrocardiogram was normal.No anaesthetic can be considered as a pure pharmo-

cological experiment, and it is unwise to draw a firmconclusion from one isolated case. I have never

encountered any adverse reaction from the administrationof mephentermine, however, whether the patient werehaving halothane or not. Had the tachycardia beeninduced by the direct action of halothane on the ven-