nS'TRMIMENT'IN HEAUH'f 1 ^" '^, mmm: * — 1 ., \ ^V 'l^^:i ^ \t Olhp i. B. 'Mi ICtbrarg North (Earolina g'tatp Imopraitg SF285 A8 V.3 The HORSEMAN'S Book Shop Old-fijoM and TUun Sookit 122 NORTH CHICAGO AVE. FREEPORT. ILL. m 4 1988 ■>.; - t 1*4 1994 THE HORSE ITS TREATMENT IN HEALTH AND DISEASE Digitized by tine Internet Arciiive in 2009 with funding from NCSU Libraries http://www.archive.org/details/liorseitstreatm03axej THE ANTERIOR AORTA AND ITS aRANCHES THE ANTERIOR AORTA ANI? ITS BRANCHES 1. Stenio-tliyio-livoitleii.s imiscle. 2. Steriio-iiiaxillans muscle. 3. Thyroid gland. 4. Parotid gland. 5. 5. Trachea. 6. Jugular vein. 7. Carotid artery. 8. 8. (Esophagus. 9. 9. r^ongus colli muscle. 10. Vertebral artery. 11. Superior cervical artery. 12. Anterior dorsal artery. 13. Inferior cervical artery. 14. E.xtenial thoracic artery. 15. Internal thoracic artery. 16. A.xillary artery. 1 7. Anterior aorta. 18. Posterior aorta. 19. Aorta. 20. Pulmonary artery. 21. Left coi-onarv artery. 22. Pulmonary veins. 23. Posterior vena cava. 24. Heart. 25. Vena azygos. 26. Subcostal artery. 27. Union of retrograde and vertebral arteries. 28. Occipito-muscular artery. THE HORSE ITS TREATMENT IN HEALTH AND DISEASE WITH A COMPLETE GUIDE TO BREEDING TRAINING AND MANAGEMENT Edited by PROF. J. WORTLEY AXE, M.R.C.v.s. ICx-President of the Royal College of Veterinary Surgeons Late Lecturer at the Royal Veterinary College, and at the Agricultural Colleges of Downton and Wye Cliief Veterinary Inspector to the Surrey County Council Consulting N'eterinary Surgeon to the British Dairy Farmers' Association Author of " The Mare and Foal " " Abortion in Cattle" " Anthrax in Farm Stock " *' Kxannnation of Horses as to Soundness " " Glanders, its Spread and Suppression " " Swine Fever " " Lithotomy or the Removal of Stone from the Bladder of the Horse " DIVISIONAL VOLUME III LONDON THE GRESHAM PUBLISHING COMPANY 34 SOUTHAMPTON STREET, STRAND CONTENTS DIVISIONAL-VOLUME III Section IV.— HEALTH AND DISEASE (Continued) 3. The Urinary Apparatus (continued) — Morbid Condition of the Urine (continued) — Page Albumen 345 Mucus - - ..... 345 Casts- .... 345 Oxalate of Lime ...... . 346 Diabetes, Polyuria, or Profuse Staling ... . . 346 Hematuria, or Bloody Urine 347 Disease of the Kidneys 348 Inflammation of the Bladder — Cystitis 349 Eetention of Urine 350 Incontinence of Urine 353 Stone in the Bladder 353 Composition of the Urine 353 Origin of Stone -...----..- 354 Composition of Vesical Calculus 355 Symptoms of Stone - - . - 356 Treatment ------- .... 359 Internal Remedies .-----...- 360 Injection of Stone Solvents into the Bladder - . . . . 360 The Operation of Lithotomy - - - - - - - - 361 Preparing for the Operation - - - - - - - - 361 E.xploring the Bladder 363 Dilating the Urethra and Cervix Vesica 363 Lithotripsy ...--- 366 CONTENTS Page The Operation ----------- 367 Vesical Calculus in the Mare 368 General Considerations on the Structure and Formation of Calculi - 369 Inversion of the Bladder 371 The Nervous System — The Cerebrospinal System 373 The Sympathetic System --------- 37i Structure of the Cerebro-Spinal Nervous System - - - 378 The Nerve-Cells 378 The Nerve-Fibres 379 The Spinal Cord 380 The Bulb, or Medulla OblongaU 382 The Pons 383 The Brain - - - 383 Functions of the Nervous System 386 Cerebro-Spinal Nerves 391 The Cranial or Encephalic Nerves - - 391 Spinal Nerves - ... 397 Brachial Plexus ---... 398 Lum!)o-Sacral Plexus 402 Diseases of the Nervous System .--.... 405 Cerebritis and ftlenirigitis ----....- 405 Vertigo ....- 407 Abscess in the Brain - - - - 409 Epilepsy . - 410 Eclampsia - - - ■ - - - . - - . -.ni Chorea (St. Vitus' Dance) - - 411 Stringhalt - - . . -411 Apoplexy -412 Crib-biting 413 Tumours in the Brain and Cranium - • - <> - - .415 (Edema of the Choroid Plexus - - - ■ - - - 41 6 Exostoses, or Bone Tumours 417 Thickening of the Membi'anes - - - 417 Diseases of the Spinal Cord and its Membranes 418 Acute Spinal Meningitis — Inflammation of the Memliranes of the Spinal Cord 418 Acute Myelitis — Inflammation of the Spinal Cord - - - - 418 Paralysis -_- - - - -419 Hemiplegia 420 Paraplegia, Spinal Paralysis 421 Peripheral or Local Paralysis 422 Cerebro-Spinal Meningitis 433 CONTENTS V 5. The Absokkent Systkm— Page Definition - - 425 The Lactejil System . . . 4-_'0 The Lym])h;itie System - - - A2H The Lymplialii- (Hands - 428 6. The Organs of Circulation — The Blood - - 430 The Coagulation of the Blood 435 The Mechanism of the Circulation ...... 436 The Nerves of the Heart 440 The Blood-vessels . . . 441 The Pulse 443 The Contractility of the Arteries . . . - . . 443 Blood Pressure ----------- 444 Prevention of Death by Hemorrhage 445 The Capillaries - - ..----. - 446 The Chief Arteries and Veins -.-..-.. 447 Distribution of the Systemic Arteries ...... 448 Diseases of the Heart --.....-. 453 General Consideration of the Pathology of Heart-Disease - - - 453 Physical Examination of the Heart --.---. 458 Pericarditis — Inflammation of the Heait Sac . . . . . 461 Endocarditis — Inflammation of the Lining Membrane of the Heart - 463 Myocarditis, or Inflammation of the Muscular Structure of the Heart- 464 Diseases of the Valves of the Heart ---... 464 Hypertrophy — Enlargement of the Heart 465 Atrophy of the Heart .-.-....- 467 Fatty Disease of the Heart .--....- 467 Rupture of the Heart .-.---. . . 470 Diseases of the Arteries and Veins ...... 471 Arteritis .... ..-....- 471 Atheroma (Endarteritis Deformans) ..-.-. 472 Thrombosis ....-..--- 473 Iliac Thrombosis . . . - 474 Thrombosis of the Jugular Vein (Phlebitis) .... - 475 Aneurism ------------ 477 Diseases of the Blood 478 An;emia -.-.-----.-- 478 Plethora - 480 Septica-mia .....--.-- 481 viii CONTENTS Page 7. The Orcaxs of Respiration and the Respiratory FRocEssi — Descrution of the Respiratory Process 482 The Lungs 484 The Larynx 485 The Trachea .--.-- ... 485 The Bronchi 486 The Air-Ceils .... 486 Effects of Respiration .... . . 437 Composition ot the .Vir ... 487 Air after Respiration ----...... 488 Air-changes iti the Blood 489 The .Mechanism of Respiration ....... 491 The Nerves and Xerve-Centres of Respiration 494 .\SPHYXIA 494 Ventilation 495 Diseases of the Respiratory Organs 497 Catarrh or Cold --....... 497 Chronic Nasal Catarrh — Nasal (jleet 499 Hemorrhage ---.-. ..... 501 Bleeding from the Nose — Epistaxis -.-.... 503 Pus in the Guttural Pouches --.-.... 504 Diseases of the Larynx 507 Laryngitis ---........ 507 Roarini; and Whistling 510 ILLUSTRATIONS DIVISIONAL-VOLUME III FULL-PAGE PLATES Page The Anterior Aorta and its Branches (colour) - - Fwutispiece Operation for Stone - - - - - . 364 Calculi - - 370 Nerves, Arteries, and Muscles of the Limbs — I (colour) - ■ - 390 Nerves, Arteries, and Muscles of the Limbs — II (colour) - - - 398 Anatomy of the Horse's Head (colour) 402 Brain Tumour — QiIdema of Choroid Plexus (colour) 414 Cerebro-Spinal Meningitis and Arteritis (cohmr) ----- 424 Distribution of the Arteries — I (colour) ------- 448 Distribution of the Arteries— II (colour) ------- 452 Valvular Disease of the Heart ------- 464 Thrombosis - - - 47-1 TEXT ILLUSTRATIONS Casts in Horse's Lrine - - - 345 Crystals of Oxalate of Lime from Horse's Urine . - - - 345 Retention of Urine in the Mare — Pass- ing the Catheter - - - - 351 Retention of Urine — Catheter in- serted ------ 352 Stone overgrown with Gi'atmlation Tissue ------ 358 Stone empouched in the Fundus of the Bladder ------ 358 Stone empouched in the Fundus, and extending into the Cavity of the Bladder ------ 350 Page Grooved Staff ----- 362 Lithotomj' Knife (sharp-pointed) - 362 Lithotomy Knife (blunt-pointed) ■ 362 Whalebone Pi-obe - - - - 362 Dilator ------ 363 Spike-faced Forceps - - - - 364 Drainage Tube ----- 366 Perineal Needle ----- 366 Lithotrite ----- - 367 Forceps for Lithotripsy - - - 367 Scoop ------ 368 Sound ------ 368 Vesical Calculus ----- 369 Sections of Vesical Calculus - - 370 ILLUSTRATIONS Inversion of the Bladder - Ganglion Cells of the Sympathetic Xerve of the Muscular Coat of the Bladder Diagram of the Ganglia of the Sympa- tlietic Sj'stem of Nerves - Nerve-Cells Section of Nerve ... - The Spinal Cord . . . . Sections of Spinal Cord Under Surface of Horse's Brain - Upper Surface and Horizontal Section of the Bi'ain - - - - . Longitudinal Section of the Brain Sleepy Staggers - - . - ■ Vertigo, or Megrims - - - - Throat Strap for Crib-biting Facial Paralysis ----- Sketch of the Lymphatic Vessels of the Fore -Leg ----- Section through the Small Intes- tine -.-..- Section of Lymphatic Gland Blood Corpuscles - - - . Crystals of Haemoglobin Colourless Blood Corpuscles, showing Page 372 374 375 378 379 381 381 382 384 385 406 408 413 422 426 427 429 431 433 successuc changes of outline during a period of ten minutes - Horse's Heart . - - - - Diagrammatic A'iews of the Heart Section of the Heart, showing the Val- \ular Apparatus . - - . Transverse Section through a small Artery and Vein - - - - Diagram of Circulation Fatty Infiltration of Muscle Fatty Degeneration of Muscle Aneurism of the Aorta The Lungs in their Natural Position - The Larynx - - - . - The Larynx, seen from above The Lungs and Bronchi Sack-like Fnds of a Bronchiole - InsutHator ------ Fumigation of the Nostrils for Catarrh Transverse Section of Horse's Head, showing the Guttural Pouches Concretions of Pus fi'om the Guttural Pouches ------ Tracheotom3'Tul:ie inscited in thc^\'ilul- pipe ------ Larynx of a " Roarer " - - . P.i(;e 434 437 438 439 442 450 468 469 478 483 484 4S5 486 487 500 501 505 505 509 510 MOKBID CONDITION OF THE UKIXE 345 ■■ B IV^^I l^n HQ ^^^mM^^ ^i^^^^^i ^^^^^1 ^^H^^rCi^H H^^^Hr - '^i-^- #^^^H D^^l ^^n H^^^^H ^^Isb ■■Ij^^v^'^^^'/ ■ '•!"'^;'''^ ^^^^^^^H ^■■^ ^B^^ ■■•j-<'- £ - ' -\' ^1 ~^^Hi^^B ^^K^^^^ °^^m • ■" V'O'' '■•'■■■ ^B K ^I^^H^A ^^kP-^l LoW ■-.■■■ (9' /' ■ ■ -v ,^1 ^ ^^P M ^^°°l h^ - '€# '-''^.;.°''.^H wA ^^^^m ^^^H Fig. 143. — Casts in Horse's Urine JIucous casts. B, Small waxy clear casts, c, Casts with fat and oil globules. D, Large granular casts Albumen. — This suKstance is not a constituent ot healthy urine, al- though it is sometimes found as a temporary contamination. When exist- ing as a permanent condition it is a matter of serious imjjortance, inasmuch as it indicates the existence of organic disease of some j)art of the urinary apparatus, most frequently the kidneys. Albumen is recognized by adding to a small quantity of the suspected urine, in a test-tube, a few (hops of nitric acid, when the albumen, being coagulated, falls to the bottom of the glass as a grayish Hocculent deposit. Boil- ing also produces the same efiect. Mucus. — The whole of the urinary channels being lined by mucous membrane, it is not re- markable that mucus should be found in healthy urine. Some- times, however, it exists in such amount as to render the fluid thick and ropy, and to impart to it the consistence of thin glue. This condition is not neces- sarily associated with serious organic disease, but rather with a .state of irri- tability of the urinary organs generally. It is most frequently seen in old animals, and especially mares. When submitted to microscopical exami nation the urine in these cases is found to contain small mucous corpuscles en- tangled in a sticky Huid, together with a number of fine filaments studded with minute granules of carbonate of lime. The latter are derived from the kidney, and represent casts of the urine tubes in which they have been formed. Casts. — In addition to mucous casts, just referred to, others of various com- j^osition are met with as the result of infiammatory disease of the kidneys. Of these some are composed of epithelial cells in various stages of decay, shed from the inner surface of the urine tubes; others are formed of blood corpuscles either alone or mixed with, or enclosed in, epithelial cells, while others are .structureless and wax-like (fig. 143). » Vol. I. 24 Fig. 144. -Crystals of Oxalate of Lime from Horse's Urine 346 HEALTH AND DISEASE Oxalate of Lime, altliough frequently occurring in the urine of healthy horses, is now and again found to exist in large quantities, associated with a disease of an obscure character, to which, for want of a better name, " oxaluria" has been applied. In a case recorded by the late Professor Morton the urine was found to contain this salt in con- siderable amount (fig. 144). When first examined, Professor Morton says the pulse was found to be thirty-two in a minute, tone feeble, a peculiarly anxious countenance was observed, and a looking from time to time to the loins, with an ex- pression indicative of pain. The appetite was impaired and capricious, although there was but little loss of flesh. On walking the animal out of the stable, considerable languor and listlessness were evinced, and the slightest exertion produced great fatigue. On his being returned to the stable he immediately placed himself in the position to urinate, and, after making several ineffectual attempts, a few ounces of urine were voided, having a very peculiar smell, and being somewhat viscid. In this case the urine had a light amber colour, and was clear. It gave an acid reaction to test-paper, and its specific gravity was 1 '00045. It did not contain albumen, but when examined microscopically was found to contain a large amount of oxalate of lime, in the form of bright octahedral crystals. The presence of oxalic acid in the urine is believed to arise out of some defect in the digestion and assimilation of the food. DIABETES, POLYURIA, OR PROFUSE STALING Definition. — A morbid activity of the kidneys, resulting in an ex- cessive secretion of urine. Diabetes assumes two forms, distinguished as diabetes mellitUS and diabetes insipidus. The former is characterized by the presence of sugar in the urine, and an increase in the specific gravity. In the latter there is an absence of sugar, and the specific gravity is usually below the normal standard. Diabetes mellitus is rarely seen in the horse. Causes. — Profuse staling, or polyuria, is sometimes associated with indigestion and suppressed skin function. Hay that has been badly harvested, and by exces.sive fermentation become heated and " mowburnt", is one of the most frequent causes of the disorder, while in other cases the drinking water may be at fault. Foreign oats and hay are more frequently found to affect the urinary organs of horses in these islands than those grown at home. Debility and exposure to great vicissitudes of climate are also considered as a probable cause. The disorder is usually found to exist without any organic disease of the kidneys themselves. H.-E.MATUKIA OK BLOODY UKIXF. 347 Symptoms. — In addition to the excessive quantity and the frequency with which the urine is passed, marked thirst is a prominent and lasting symptom. The pulse is weak, the skin loses its gloss, becomes dirty and closely "bound" to the parts beneath. The membranes of the eyes and nose are pale in colour, the appetite capi-icious, and the breath sour- smelling. The aft'ected animal rapidly loses condition, and sweats under comparatively slight exertion. Moreover, the capacity for work is largely curtailed. The urine, besides being light in colour, has a low specific iiravity. Treatment. — In the early stage, and before excessive debility is present, a mild aloetic aperient may be given as a preliminary measure, and this should be followed by a demulcent diet, consisting largely of linseed tea, with scalded oats of the best description, and good sound bran. The so-called diuretic remedies should in no case be prescribed. Gallic acid or powdered nutgalls, with nux vomica and quinine, may be recommended. This failing, a course of iodide of iron should next be tried, and upon an abatement of the symptoms may be advantageously replaced by a mixture of nitro-hydrochloric acid and infusion of calumba. Belladonna, in the form of extract or tincture, is recommended in cases of some standing. The food should be of the best, and an unlimited quantity of drinking water allowed. The patient will be benefited by a short period of walk- ing exercise in the middle of the day. On no account should he be exposed to wet, or to cold easterly or north-easterly winds. A warm but well-ventilated stable should be provided, and the surface circulation maintained by ample clothing. With proper treatment a few weeks suffice to bring about complete convalescence. HtEmaturia or bloody urine Urine may become contaminated with blood from various sources. In all cases, however, this condition denotes broken blood-vessels, either as the result of disease or accident. As to the precise seat of the lesion, some sort of opinion may be formed by noting the manner in which the blood is discharged. When coming from the kidney it is uniformly mixed with the urine. If the hemorrhage is from the bladder the blood-stained portion of the urine will most frequently be the last passed in the act of micturition, its greater specific gravity causing the blood to sink to the lowest portion of the organ, and only to be expelled at the final muscular contraction of the viscus. When the source of blood arises from injury to the urethral canal, it is washed out with the first portion of fluid issuing from the bladder. 348 HEALTH AND DISEASE Causes. — Some cases of bloody urine are caused by injuries, the result of external violence; others may be traced to the presence of calculi (stones) in the kidney or the bladder, and occasionally also in the urethral canal. Structural changes resulting from one or other of the various diseases aflectiiig these organs are accountable for a small percentage of cases. Treatment. — When hemorrhage is the result of the presence of stone in the bladder or urethral canal, the offending body must be removed by operation. If it arises in the course of disease of the kidney, cold cloths should be applied over the loins, and small doses of tannic acid, with nux vomica, administered two or three times a day. The patient will require to be kept perfectly quiet, and the bowels maintained in a state of activity by light bran diet and two or three tablespoonfuls of linseed-oil morning and evening. Enemas of cold water will also assist in keeping the bleeding in check. Demulcent drinks, as linseed tea, should take the place of water, but the quantity allowed should not be excessive. DISEASE OF THE KIDNEYS Nephritis. — Inflammation of the kidneys of the horse is much less frequent than in man — a ditlerence which no doubt finds explanation in the absence in the one of those serious dietetic and alcoholic abuses which are so commonly prevalent in the other. Causes. — Chief among these are exposure to cold and wet while the body is heated and fatigued. It is often induced by the hal)itual administration of cantharides to excite the sexual instinct in travelling stallions. The abuse of diuretic agents, as turpentine, resin, nitre, and oil of juniper, undoubtedly contributes to the number of cases of inflamed kidneys, and it may be accepted as true that the less knowledge carters and grooms possess of the horse, the more frequent will be their use of drugs, and the more powerful those selected. Inflammation of the kidneys may also result from inflammation affecting the bladder, by extension of the disease along the line of the ureters, or from absorption of cantharides into the blood when applied over large sur- faces of the skin for blistering purposes; and it sometimes follows certain forms of blood-poisoning, during which the blood-vessels become blocked, and abscesses develop in the structure of the gland. Severe strains in jumping, and violent efforts at draught, are probably sometimes provo- cative of the flisease. Symptoms. — In this affection the patient shows a frequent desire to stale, but the (juantity of urine expelled at any one time is very small. INFLAMMATION OF THE BLADDER -CYSTITIS 349 and the total amount di.scluirgeil in the twenty-four liouis is niucli less tluin usual. Attempts to urinate are sometimes made without eti'eet, and the penis is unsheathed and retracted from time to time without any attempt to stale being made. Now and again colicky pains appear, and the animal is restless and essays to lie down. The urine is thick and muddv, and sometimes blood-stained, or it may become charged with pus. Pressure over the loins causes the animal to cringe, and the hind-limbs are moved somewhat stiffly in progression. As the disease advances there is marked constitutional disturbance, shown bv the quick pulse, accelerated breathing, increased temperature, hot and clamnn' mouth, and the occurrence of patchy sweats. Rigoi's are sometimes present, the face wears a pained and anxious expression, and the mucous membranes of the eyes and nose are intensely reddened. Treatment. — This should be commenced by the administration of aloes sutticient to open the bowels freely. The diet should be reduced to bran, with which a little boiled linseed may be mixed, and the tea from the latter ^vill prove a most desirable drink, to which, if possible, the patient should be contined. AVhere pain is severe, opium may be administered in small repeated doses. Hot cloths to the loins will exercise a soothing in- fluence, and enemas of warm water in which a little extract of belladonna has been dissolved will materially aid in subduing existing inflammation. Where, as sometimes occurs, there are no conveniences for fomenta- tions, the loins may be stimulated by means of soap liniment and strong ammonia {liquid ammonia). On no account are turpentine and cantharides to be used as local applications. Their absorption into the blood would inevitably aggravate the disease. INFLAMMATION OF THE BLADDER— CYSTITIS Definition. — An inflamed condition of the lining membrane, extending more or less to the other structures of the bladder. Causes. — This disease is the result of some irritant acting upon the mucous membrane by which the organ is lined. The provocative agents are sometimes mechanical, at others they are of a chemical nature; of the former, stone in the bladder is the more common cause. Chemical irritation results in those cases where the urine is long retained, either as the result of paralysis or otherwise, and in consequence undergoes decomposition. It also follows upon the too- free administration of can- tharides and croton-oil, or from their absorption by the skin when applied over a large surface. In mares, it may be the result of difficult parturi- tion, where much force has ))eeu employed in extracting the fretus. In- 350 HEALTH AND DISEASE flammation of the bladder sometimes comjjlicates certain forms of influenza, and attends the development of morbid growths. The symptoms are those of abdominal pain with frequent shifting of the hind-feet. Urine is discharged in small quantities and often, and the affected animal repeatedly extends himself as if to stale, without effecting his purpose. The penis is unsheathed from time to time and again re- tracted ; this symptom is particularly marked when the disturbance is caused by cantharides or other sexual irritants. In mares the vulva is spasmodic- ally everted from the same cause. If the bladder be pressed upon by pass- ing the hand into the rectum the animal evinces pain by looking round towards the flank. The urine is usually turbid or muddy, and may be blood-stained. Unless relief is afforded, the pulse becomes quick and small, the breathing accelerated, the mucous membrane of the eyes changes from a pale pink to a brick-red hue. The countenance wears a pinched and haggard expression, and general prostration becomes marked and severe. Treatment should be directed to subdue existing pain and render the urine as little irritating to the inflamed organ as possible. With the latter object bland soothing fluids, consisting of linseed tea, milk, barley- water, and white of egg, should be given. The bowels must be freely acted upon by a dose of aloes, and enemas of warm water, in which a little extract of belladonna and glycerine has been dissolved, will require to be administered two or three times a day. Nothing contributes so much to the relief of the patient as to guard against the accumulation of excrement in the posterior bowel. In some cases it is most desirable that the bladder be washed out from time to time with a warm antiseptic solu- tion, in the preparation of which carbolic a<'id or perchloride of mercury will be found the most suitable agents. This, however, being an operation requiring special knowledge, should not be attempted by an amateur. Small, repeated doses of belladonna will be found most useful in reducing the pain and irritability of the diseased organ, and some relief will also be afforded by hot cloths applied across the loins. Horses having once suffered from inflammation of the bladder are liable to a recurrence of the disease, to avoid which they should be afforded frequent opportunities to stale. RETENTION OF URINE Definition. — Partial or complete inability to expel urine from the bladder }i\' the usual natural method. Causes. — It is frequently due to spasmodic constriction of the neck of the bladder, and may also be the result of mechanical obstruction in RETENTION OF UKINE 351 the urethral canal. It sometimes occurs as a result of paralysis following on abnormal conditions of the brain and spinal cord. Among the meclianical obstructions may be mentioned enlargement of the prostate gland, the descent of calculi from the bladder into the urethral canal, stricture, morbid growths, swelling of the sheath, &c. Want of opportunity to stale is another frequent cause, as when thoughtless persons drive long distances and neglect to take the animal out of harness. It may be men- Fig. 145. — Retention of Urine in the Mare — passing the Catheter A, Bladder, B, Catheter. C, Valve overlapping entrance to bladder. D, Vagina. E, Uterus. F, Rectum. tioned, inter alia, that while some horses will almost insist upon pulling up for the purpose of passing urine, others require perfect quietude, and can only be induced to stale by taking them on to a straw bed. It is occasion- ally found that a horse will not relieve himself while on a journey, although taken out of a carriage, unless the bridle is removed or the breeching. The inability to pass water after compulsory retention arises out of a temporary paralysis of the mu.scular coat of the bladder, the result of undue stretching. Symptoms. — Repeated but unsuccessful attempts to urinate, standing with the front and hind legs far apart, straining, grunting or groaning, and possiblj^ the passing of a few drops of urine, which seem rather 352 HEALTH AND DISEASE to leak away than to be the result of effort. Rectal examination will confirm the diagnosis if any doubt or difficulty exists in determining between retention and non-secretion of urine. In the former condition the bladder can be distinctly felt to be distended with Huid, and in some cases the pressure of manipulation adds just sufficient force to expel a portion of it. In the latter the organ is more or less empty. Fig. 146.— Retention ; { ■ Uki msLitcJ A, Citheter. B, Bladder, c. Corpus spongiosum. D, Corpus cavemosum. E, Scrotum. F, Testicle. G, Ureter. H, Kidney, i, Aorta. J, Rectum. K, Anus. L, Prostate gland. M, Colon. Treatment. — If the urine has been long retained, and the bladder contains a large quantity, the catheter should be passed and the greater portion drawn off. Should there be indications of pain afterwards, warm fomentations to the loins, or a large poultice over that region, will have a soothing effect, and this may be increased by the admixture with it of extract of belladonna. The animal should be warmly clothed, and a do.se of two or three drams of camphor dissolved in linseed-oil may be given, followed in two or three hours by one or two dram doses of extract of belladonna dissolved in linseed tea. Every inducement to urinate should be offered by placing the patient in a well - liedded loose-box undis- turbed by other horses or their attendants. When retention of urine is STONE IN THE BLADDER 353 connected with swelling of the sheath, the latter should undergo thorough cleansing with soap and water, and be afterwards lubricated with oil or vaseline. In extreme cases scarification with a small lancet may be called for. Incontinence of Urine. — Here there is an inability to retain urine, which is discharged involuntarily, and cannot l>e controlled by the patient. Causes. — This may be due to a relaxed or paralytic condition of the musi'le which guards the neck of the bladder, and ordinarily prevents the urine from passing out; it may also result from injuries, morl)id growths, or the partial blocking with calculi. Treatment. — If caused by a mechanical impediment it may sometimes be removed by the passage of a catheter into the bladder, or by the forcible injection of fluids from a syringe into the urethral canal. AVhere a calculus exists in the urethral passage it may require a surgical operation. STONE IN THE BLADDER Composition of tlie Urine. — At the time of its discharge the urine of the horse ditl'ers in its appearance on different occasions. In colour it varies from a pale-yellow to a deep brownish-yellow. It is usually trans- parent, but frequently turbid, and occasionally distinctly muddy and opaque. It has a strong, disagreeable odour and a saltish taste. When allowed to rest, a dullish gray precipitate is thrown down, consisting chieriv of calcic carbonate (fig. 1.34). Its reaction is alkaline, and on the addition of an acid, free effervescence is induced. The specific gravity varies between 1'015 and 1"050. Microscopically examined, the sediment thrown down in repose is found to be made up chiefly of spherical, oval, and dumb-bell crystals of calcic carbonate, occa- sionally also octahedra of calcic oxalate, with a few epithelial cells from various parts of the mucous tract of the urinary apparatus. The following two analyses given by Von Bebra show the composition of the secretion: — I II Water 885-09 912-84 Solid constituents 114-91 87-16 Urea 12-44 8-36 Hippuricacid 12-60 1-23 Uric acid ... ... ... ... — — Mucus 0-05 0-06 Alcohol extract 25-50 ... 18-26 Water extract 21-32 19-25 Soluble salts 23-40 Insoluble salts ... ... ... li 40 1 80/ 40-00 354 HEALTH AND DISEASE The sediment obtained after the fluid has been allowed to rest is shown by three analyses to consist of organic and inorganic matter in the following proportions: — I n in Carbonate of lime ... 80-9 87-2 87-5 Carbonate of magnesia ... 12-1 7-5 8-5 Organic matter ... ... 7 0 5 3 4-3 100-0 1000 100-3 It will be seen from the above that urine is a highly complex fluid, comprising organic and inorganic constituents in a state of watery solution. Origin of Stone. — On the origin of vesicular calculus there is very little of a definite nature to be advanced. It is a well-established truth that under certain local as well as general conditions of the body the renal secretion undergoes various modifications and changes both in its physical state and chemical con.stitution. Thus, normal constituents may be in- creased or diminished, or altogether disappear, while others foreign to the secretion are sometimes found entering into its composition. These departures from the general standard are in some cases doubtless connected with physiological deviations in the complex processes of assimi- lation, and in some measure also with chemical alterations which the urine undergoes after its departure from the kidneys. In diseased conditions of the system peculiar compounds are not un- frequently formed which are rarely or never produced in the healthy organism, and, being feebly soluble in urine, are immediately deposited in a solid form from that fluid. In this manner oxalate of lime comes to form a part, and in some very rare cases the whole, of the vesicular calculus in the horse. To what extent the superabundant formation of lime-salts in the economy is referable to food, water, climate, and assimilative disturbance, separately or together, we have at present but little to guide us to a satis- factory conclusion. The fact remains, nevertheless, that some horses eliminate from their systems an amount of calcic carbonate that is simply astonishing. The writer's attention was recently called to a case in which a considerable amount of this salt was periodically removed from the bladder of a mare in addition to that which escaped with the urine in the act of micturition. On this subject the late Professor Morton remarks: "The water drunk by animals has generally been considered as the source of calculi, but it is by no means proved, that in those localities where lime is more abundantly met with in water, as Matlock, Scarborough, Carlsbad, and other limestone districts, that in those, calculous afl"ections are most prevalent; whereas STONE IN THE BLADDER 355 we do know that animals kept on any of the lime plants for a long time, or pastured where lime has recently been laid, become the subjects of these accuumlations. Nevertheless, excess of lime in water will readily furnish the requisite calcareous matter." Why the salts of the urine should cease to be held in solution by the urinary secretion may be conceived to arise either out of a supersaturated condition of that fluid or from chemical reactions resulting in the produc- tion of insoluble compounds, but it is not always so easy to comprehend the reasons which in certain cases determine the aggregation of small particles of salts and the development of a distinct calculous formation or stone. Such a state of quiescence as is aiforded by a paralysed bladder would appear to favour the separation and aggregation of the crystallizable constituents of the urine, as would also its retention for long periods in the cavity of the bladder, either as the result of habit or by force of stricture of the urethra, prostatic enlargement, or other like interferences with its proper and due discharge, but it cannot be said that stone in the bladder is specially prevalent under these circumstances. Experience gives no encouragement to the idea that the tendency to stone formation is greater in proportion to the amount of stone-forming salts secreted by the kidneys. Composition of Vesical Calculus. — The following table of analyses of vesical calculus of the horse and ass is given by Furstenberg: — Horse. Ass. Yellowish White. Brown. Brown. White Hard. Sediment- ary Form. Yellowish White. Yellowish Brown. Wliite Hard. Specific gravity 2-231 2-104 2-017 2-245 2-076 2-213 1-767 2-257 Carbonate of lime ... Carbonate of magnesia Oxalate of lime Phosphate of lime . . Ammonio-phosphate\ of magnesia / Silicic acid 87-10 3-63 2-10 5-45 1-721 Trace. / 83-25 5-73 2-60 6-67 1-75 61-55 8-97 17-57 4-32 5-95 1-64 85-03 3-62 5-81 4-21 1-33 84-30 8-34 5-95 1-41 69-90 6-75 4-44 4-37 12-75 1-79 67-75 9-93 10-25 10-95 1-12 80-3 15-5 Trace. 2-9 1-3 Organic matter Water and loss 100-00 100-00 100-00 100-00 100-00 100-00 100-00 100-0 Calculi, it will be seen, are composed of earthy salts in combination with a greater or less amount of organic matter. As shown by reference to the above analyses, carbonate of lime constitutes over 80 per cent of 356 HEALTH AND DISEASE the whole. Vesical calculi in the horse are strikingly uniform in com- position, and in this respect contrast greatly with similar formations in omnivorous man, in whom they are also more frequent. In him the urine contains a greater number and variety of crystallizable substances, several of which, both separately and in combination with others, assume the form of stone. Hence we have calculi of uric acid, urates of soda, ammonia, and lime, as well as others of calcic acetate, triple phosphate, and various com- binations of these renal salts. Symptoms of Stone. — The symptoms attending the existence of vesical calculus are far from uniform, either in their number, nature, or intensity. In some cases they are few, slight, and dubious, while in others they are many, pronounced, and easy of interpretation. The very slight physiological disturbance sometimes seen in stone disease has, in many instances, disarmed suspicion and frustrated detection, thus serving to sustain the prevailing idea that stone in the bladder is a disease of extreme rarity, a conclusion there is reason to think is too generally accepted by veterinary practitioners. Vesical trouble arising out of the presence of stone is mostly exhibited, in the first instance, by frequent attempts at staling, some of which are abortive, and others more or less imperfectly and with difficulty accom- plished. The urine is discharged in small quantities at brief intei-vals, and the completion of the act is signalized by a deep grunt indicative of pain. The desire to empty the bladder is more frequent and urgent during and after exertion, and particularly marked when the pace has been quick. Every now and again, while at work, the affected animal dwells in his move- ment and essays to stop. If permitted to do so, the body is at once extended, and a small quantity of urine discharged. Where the calculus is large, rough on its surface, and free to move in the cavity of the bladder, blood appears in the urine as the result of exertion. Whenever, therefore, exertion is immediately followed by the appearance of blood in the urine, the case should be regarded with suspicion, unless some other and moie obvious cause is revealed. In some instances the penis is projected from the sheath, and again retracted, at short intervals, and we have seen it remain extruded in a pendulous condition during the whole period of the disease, and to return again only after the operation of lithotomy. The discharge of urine is sometimes effected in a continuous stream, sometimes the flow is suddenly interrupted by the calculus blocking up the neck of the bladder, and occasionally it passes away involuntarily in small quantities. After the. bladder has been freely emptied, the anus undergoes a repetition of spasmodic contractions. Now and again the stone becomes impacted in the neck of the bladder, or, if a small one. may escape into and STONE IN Till'; iJLADDKR .-iSV 1)6 arrested in the urethra, resulting in obstruction and over-(li.stensi(jn of the organ, with the usual train of symptoms indicative of abdominal pain. In some examples of the disorder the gait during progression is wide and straddling, and when at rest the hind-limbs are occasionally raised from the ground as if in pain. The diagnosis is, in the majority of cases, unattended with difhculty where proper methods of enquiry are pursued, but, as we shall presently show, the detection of stone sometimes taxes the resources of the ablest diagnostician. Tumours in the bladder, croupous cystitis, organic disease of the kidneys, and various other ailments pertaining to the urinary recep- tacle may, and do, occasion symptoms only distinguishable from those of calculous disorder by a careful and searching exploration of the bladder per rectum, and by catheter or sound through the urethral canal. In regard to this latter part of the enquiry it need hardly be urged that upon it the diagnosis mainly depends. Exploration of the bladder per rectum seldom fails to reveal to us any decided enlargement occurring within or without it, but the tact and discrimination of the surgeon is often sorely tried in distinguishing between a calculus and certain forms of tumour which now and again present themselves there. In searching for stone, the mind, and with it the hand, naturally turns to related organs, and, remem- bering the possible enlargement of the prostate gland, seeks first to deter- mine the condition of this organ in particular whenever vesicular calculus is suspected. Tumefaction of the prostate is fortunately not difficult of recognition. The backwardness and fixed condition of the swelling, its intimate connection with the neck of the bladder, its peculiar outline of form and yielding nature, serve at once to distinguish it from stone. Tumours in the bladder usually disclose themselves by their diftuse, and maybe also by their lobulated and fixed condition. The bladder should now be explored by means of a long sound passed through the urethra, assisted, in the case of a horse, by the hand of the examiner passed into the rectum. In searching the bladder for stone the organ is allowed to become moderately distended with urine, when, first in a standing, and then in a recumbent, posture, the sound (after being well oiled and disinfected) is introduced into the urethra, and gently forced on until it enters the bladder. It is now moved slowly backward and forward with a rotatory action, so as to bring the metal point of the instrument into contact with every part of the interior surface of the bladder, the operator noting at the same time any roughness or irregu- larity of surface or resistance it may meet with, or any sound or impression it may convey. If the result is not satisfactory, the position of the patient must be changed by turning the animal first on one side and then on the 358 HEALTH AND DISEASE Fig. 147.— Stone Overgrown with Granulation Tissue other, and uow on tlie back, until every part of the bladder has been thoroughly explored. Where the substance felt per rectum is a calculus, its contact with the searcher will be clearly made known by the rough and resisting character of the touch, and by the sound emitted when struck. Even with the exhaustion of all the methods and devices which science has designed for surgical diagnosis, failure may still attend our efforts to detect a stone, and although the existence of something in the bladder be ever so obvious, its precise nature cannot always be clearly and definitely made out. In those examples of stone, partially or completely over - grown by granulation tissue (proud flesh) (fig. 147) spring- ing from around an ulcerating surface, or enclosed in false membrane, the question of stone or tumour is difficult to divine. Here the stone, hidden away in the new growth or exudation matter, is sheltered from the sound, and the instrument, striking the morbid mass, imparts to the hand precisely those impressions which denote the existence of tumour. In this uncertain and unsatisfactory condition no time should be lost in opening the urethra at the perineum, when the bladder may be again explored by means of the short metal sound, to be referred to later on. It is not alone by active changes in the bladder, such as I have just referred to, that stone is enabled to evade de- tection. Passive alterations in this organ are likewise to be borne in mind as possible ob- stacles in the same direction. The most familiar example of this anomalous condition is met with in those cases where the weight of the stone, bearing on the an- terior end or fundus of the bladder, creates for itself a diverticulum or pouch, in which it becomes lodged (fig. 148). The mucous memlirane in those instances usually constitutes the sac, it having been pushed between the widely separated and atrophied fibres of the muscular coat; less frequently all the coats enter into the saccular offshoot. In .some Fig. 148. — Stone Empouched in the Fundus of the Bladd< STONE IN THE I'.LADDEK 359 rare instances, as one recently related to me by Mr. F. Wragg of London, not only does the stone occupy the pouch, but, enlarging by accretion iu the direction of the interior of the viscus, comes also to project into the proper cavity of the bladder (fig. 149). This is an important condition to consider in relation to the success of the operation of lithotomy, as will hereafter be explained. Where the stone becomes thus encysted it may or may not be accessible per rectum in a standing posture, or to the sound through the urethra, according to the extent to which it has extended from the pelvis in the direction of the abdominal cavity. If, however, the horse be placed on his back, the stone will be caused to fall towards the spine, and thus be brought within reach of the hand. Referring again to the general symptoms of stone, it may be remarked that they undergo various modifications of char- acter and intensity, according to the size, nature of the sur- face, and the relations of the calculus with the general cavity of the bladder. Stones of large dimensions occasion much pain and sufter- ing, especially where the surface is rough and the stone free to move fi'om place to place with the movements of the body. Here the mucous membrane sufiers much irritation, and, with the muscular coat, becomes considerably thickened. As a result, the walls of the bladder lose their expanding power, and, by failing to open out for the accommodation of the incoming urine, provoke and render necessary frequent acts of micturition. Inflammation and purulent urine are among the wor.st con- sequences of a heavy rough calculus. Smooth calculi (which are rare), and such as are confined in pouches of the mucous layer, occasion much less disturbance, and may even fail to excite suspicion of their presence. Treatment. — Various methods, physiological, chemical, and surgical, have in turn been practised and extolled for the prevention and eradi- cation of stone, and each succeeding decade, with its larger experience and resource, has called forth either the condemnation or modification of the one, or the improvement and consolidation of the others. For a con- siderable period belief and reliance iu the efticacy of internal remedies was largelv entertained; but as time advanced, and the teachings of anatomy, Fig. 149.— Stone Empouched in the Fundus, and extending into the Cavity of the Bladder 360 HEALTH AND DISEASE physiology, and physics led to the improvement of surgical methods, sur- gical means, and surgical handicraft, the treatment of stone passed well- nigh altogether from the domain of the physician to the more practical and radical dispensation of the surgeon. Internal Remedies. — The internal remedies which have been recom- mended and employed in this branch of treatment have been selected purely on the ground of their chemical properties and action on alkaline carbonates out of the body. A vesical calculus, it has been argued, con- sisting as it does chiefly of calcic carbonate, should be chemically resolved by the repeated administration of mineral acids, experience in the labora- tory having taught that the decomposition of the former is readil}- and surely effected by contact with the latter; hence mineral acids were for a long time, and still continue to be, administered for the purpose of bringing about a solution of the stone. Practical experience, however, has at no time done much to confirm this time-honoured dogma, and the teachings of physiology encourage no sort of belief in its therapeutical value. Even in those instances where the operation of lithotomy is foi'- bidden by the circumstances of the case, we are not warranted by any consideration in relying on so precarious, nay useless, a remedy as the so-called stone soIrn with the finger should be made. While the left forefinger, already in the bladder, explores the neck of the organ, the right hand, acting through the rectum, will, as far as possible, force the bladder backward in order to bring a larger area of surface within reach of the finger. Here a long index finger offers a distinct advantage, and should the operator fall short in this particular, he may take advantage of such help as his most practical assistant may be able to afford him. As a rule we are only capable of manipulating the neck and parts immediately beyond it, but by means of the short metallic sound, presently to be described, we are enabled to recognize any marked alteration in the naturally smooth, satin-like surface of the lining membrane. By careful exploration we may, for example, satisfy ourselves of the existence of tumour, false membrane, calcareous encrustation of the mucous layer so often found in association wdth calculous disorder. A knowledge of the presence or absence of these morbid conditions constitutes a distinct advantage in estimating the immediate success of the operation and prospec- tive result of after-trcatmrnt. Dilating the Urethra and Cer- vix Vesica. — Having devoted a few minutes to the very interesting and instructive task above referred to, we now proceed to dilate the urethra and neck of the bladder. It is a great con- solation, when confronted with a large stone, to know that this portion of the urinary passage is capable of consider- able relaxation and dilation. Sudden and spasmodic attempts at dilation is bad practice, and should on no account be resorted to. For effecting the opening out of the urinary channel the three-bladed dilator (fig. 154), constructed on the plan of a human anal dilator, but with longer blades and with a correspondinglv large range of action, will be found effective. 154.— Dilator 3G4 HEALTH AND DISEASE This is introduced into the opening m.ule in the perineum and pushed onward towards the bladder. The handles of the instrument are now compressed and the blades caused to diverge steadily until the necessary dilation has been accomplished. The patient is now allowed to rest on the right side. The operator finds it most convenient to occupy the recumbent posture, and places himself on his left side. The form of the forceps to be employed in removing the stone will, of course, depend upon the consistence of the calculus to be removed. Where the superficial portion of the stone is found to be loose in texture, and consequently liable to crumble, the spike-faced forceps (fig. 155) should be employed. This is armed with three spikes on the opposing surface of each blade, which, on meeting the stone, pene- trates its outer weak crust, and gains a firm hold of the more dense parts beneath. Fig. 155.-Spike-faeed Forceps EsCapC from tllC grip of the instrument during extrac- tion is thus rendered difficult, and disintegration is at the same time avoided. The forceps, held in the left hand, is introduced into the bladder, and the right hand is passed into the rectum to steady and direct the stone, which will now be distinctly felt and heard grating against the instrument. Here the blades must be opened and closed again and again, with a catching movement, being also turned about first in one direction and then in another, until seizure of the calculus is effected. Should any difficulty in securing the stone be experienced in the procedure, the forceps is to be withdrawn, and the calculus brought forward by the hand acting through the rectum and held firmly against the neck of the bladder, while the blades of the instrument are slid carefully over it. A firm hold ha\'ing been secured, the operator must then assure himself that no part of the mucous membrane is grasped and included with the stone. This may be done by rotating the forceps on its axis, and moving it backwards and forwards, first in one direction and then in the other. If no impediment is experienced it is to be inferred that the bladder has not been laid hold of, and that in this respect all is right; on the other hand, should the movement of the instrument meet with interruption, the blades must be slightly relaxed and the imprisoned membrane liberated. The position of the stone, as it rests in the forceps, is next to be considered. Here we may remark that vesical calculi are almost invariably ovoid in shape, and are frequently seized across tlie short diameter, in which position PLATE XXIX OPERATION FOR STONE Fig. A. I. Catheter. 2. Stone. 3. Reauni. 4. Knife cutting into tlie Urethra. Fig. B. 1. Liihotritc. 2. Stone in the jaws of the Litliotriie. 3. Hand in the Rectum assisting in bringing the Stone into the jaws of the instrument ready for cnisliing. STONE IN THE BLADDER 365 it is at all times ditticult, and in most instances impossil)le, to extract thorn. For this reason it is of the first importance that the long diameter of the stone should be made to correspond with the long axis of the forceps. To accomplish this the calculus is drawn well up to the neck of the bladder, wluMi, with the index finger acting between the released blades of the instrument, it is carefully turned and brought into the desired position. This having been done, extraction of the stone is then proceeded with. The extracting force required to effect removal will, of course, depend upon the size of the stone in relation to the urethral orifice. Large calculi, and particularly such as are rough and catchy, require a considerable amount of traction and careful manffiuvriug to bring them away. Before attempting removal, the stone must be firmly gripped and a good hold secured by bringing both hands to bear on the handles of the forceps, whose blades should be so placed that their surfaces are directed right and left, and their edges upward and downward. A steady and continuous pull, gradually increasing in force, is now begun and continued, with a wriggling movement of the hand and an occasional slight alteration in the direction of the traction, at one time pulling slightly to the right, at another to the left, now upward, then downward, and so on. If the wound be not sufficiently large, a touch with the scalpel here and there at the points of resistance may be resorted to as a means of facilitating extraction, or an assistant may be called upon to open the wound by inserting his fingers well within its edges and pulling in opposite directions. Should the stone prove to be too large for extraction by reasonable force, crushing must be at once had recourse to. Where the calculus is loose in texture, and friable, the resist- ance of the edges of the wound to the extracting force may give rise to disintegration of the outer crust, which, breaking away, remains in the blades of the forceps, while the main body of the stone escapes into the bladder. In such an event the offending body must be again secured. Having undergone a reduction of size, less resistance will be experienced in the next attempt at removal. An additional advantage will also be gained in the firmer hold the more compact remains of the calculus allows to the forceps. Having removed the stone, the bladder will now require to be well washed out with warm carbolized water in order to cleanse it of the blood, nmcus, and earthy debris, some or all of which it is sure to contain in greater or less amount. This • operation is best accomplished by intro- ducing the three -bladed dilator (fig. 154) into the neck of the bladder, and, after moderately enlarging the orifice, forcing into the cavity a fairly strong stream of wann carbolized water out of a small enema syringe. Whether the perineal wound should be closed at once nuist depend 366 PIEALTH AND DISEASE upon the nature antl extent of disease existing in the bladder. If there is reason to think that the lining membrane is seriously ulcerated, or covered with false membrane, a distinct advantage will be gained by introducing a lithotomy tube (fig. 156) into the bladder and allowing the wound to remain open until the vesical irritation has been subdued by frequent injections ^^__ _ ^-^' of warm carbolized ..»oL».s.KiL.,oa, y^ hand, if no such com- Fig. 156.— Drainage Tube plicatioUS Bxist thcrC, A, Silver mount and rings. B, Elastic gum tube. the CclgeS of the Super- ficial wound may be brought together at once by three interrupted sutures of flexible wire, and the patient removed to his box. The irritation resulting from the operation naturally leads to much whisking of the tail, during which hairs become entangled with the wire, and the parts about the wound suffer considerable contusion ; this must be provided again.st by tying the tail on one side to a roller or some other convenient arrangement. Under ordinary circum- stances but little is needed in Fig. 157. -Perineal Needle the shapc of after- treatment. The skin below the perineum is smeared with lard or vaseline to prevent excoriation by the urinary and other discharges, and the wound is carefully cleansed and carbolized as often as may be required. An enema of warm water occasionally thrown into the rectum affords a good deal of comfort by freeing the gut from feculent matter, and removing all pressure from the sore and sensitive urethra and bladder beneath. Lithotripsy. — The operation of lithotripsy or crushing may be resorted to when the stone, though too large to be moved entii-e, is yet small enough to be seized and broken up into fragments by means of the lithotrite. In the quadruped it is not performed as in man, through the natural channel of the urethra, but through an artificial oj^ening in the urethral canal as described in the operation of lithotomy. It must, there- fore, always be regarded as supplementary to lithotomy, and depend for its performance on our inability to extract the calculus whole. In the absence of serious complications lithotripsy offers a fiiir and reasonable prospect of success. If from the first the operation is found to be necessary, the bowels should be freely opened with an aloetic purge, and the diet so ordered as STONE IN THE BLADDER 367 Fig. 158.— Lithotrito to avoid uiulue fulness of the alinientuiy canal, and facilitate digestion. An enema of warm water administered once or twice during the twenty- four hours before its performance will serve to keep the rectum empty and soothe the irritable bladder. Small doses of j^otassic bicarbonate, and opiates, if necessary, may be given at intervals where pain is indicated. The Operation. — In performing the operation of crushing, the horse is thrown as for castration, and when under the influence of chloroform the urethra is opened in precisely the same manner and place as directed for litho- tomy. The neck of the bladder is then dilated, and the lithotrite (fig. 158), nicely warmed and smeared with oil, is passed into it. The blades of the instrument are then drawn as far apart as may be necessary to receive the stone. The next step is to bring the calculus fairly between them. To accomplish this the lithotrite should be held by one hand applied near the blades, the screw being in charge of an assistant who will also steady the instrument while the seizure is being effected. With the other hand in the rectum the operator now proceeds to manipulate the stone, and by a little careful manoeuvring directs it into the jaws of the lithotrite. The assistant, on being instructed, will then turn the screw until the calculus is secured. Having obtained a good hold of the stone a half- turn is given to the litho- trite, first towards the right, then the left, so as to determine if any portion of the mucous membrane has been included in the grasp of the instrument. To obviate this it is usual in man to operate with the bladder distended with urine, but in the horse the fluid cpiickly drains away through the perineal wound, and cannot therefore be made available for keeping the walls of the organ away from the calculus. When the stone has been satisfactorily secured, the screw is brought again into action, and the operation of crushing proceeded with. This done, the broken fragments are freed from the lithotrite and removed with the forceps (fig. 159) and scoop (fig. 160), aided by repeated injections of warm carbolized water as directed for lithotomy. Should the operation prove troublesome and protracted, it may be Fig. 159.— Forceps foi- Litliotri 368 HEALTH AND DISEASP: necessary to defer completing the operation to a future day, in which case a light diet should be prescribed for a few days, say from three to seven, when tlie operation may be again renewed, and, if possible, carried to completion. In the meantime portions of stone may enter the perineal orifice and become arrested in it. These are to be carefully removed, and it may be necessary also to pass the catheter to discharge any debris which may have accumulated in the urethral canal. In addition to this the bladder will require to be thoroughly washed out once daily with Fig. 160.— Scoop warm carbolized water for the first two or three days, after which it may ])e discontinued. On completion of the operation the bladder should be carefully searched with the short metallic sound (fig. 161), and if found free from fragments of stone it only remains to remove the animal to his box. He should then be dealt with according to the rules laid down for the after-treatment of lithotomy. An opiate draught, followed by warm fomentations to the perineum with carbolized water and periodical injections of warm water into the rectum, will serve to soothe the injured parts and allay irritation. Fig. 161.— Sound Vesical Calculus in the Mare. — Mares are seldom the sulijects of vesical calculus. This immunit}' may be referred in part to the short and straight outward course of the urethra, which favours the free extrusion of solid matter with the urinary discharges. Occasionally, however, stone is found in the female organ, but not so frequently as is generally stated. Several instances have been brought to the notice of the writer where intestinal calculi ejected from the rectum have been said to have escaped from the bladder in the act of urination. The form, character, and composition of these concretions, however, were in each case sufftciently marked to enable him to decide to the contrary. The symptoms of the affection are, for the most part, the same as those described in the horse. Removal of vesical calculus in the mare is usually a much more simple and less dangerous matter than in the horse. When the stone is small the operation may in some cases be performed standing. Having made the animal secure with twitch and side-line, the STONK IN THE BLAltDEK' 369 neck of the bladder is careiully dilated and the litliotoniv foi-ceps intro- duced witli one hand, while the other, in the reetum, directs the calculus between the blades. Seizure having been effected, and the manipulative precautions already prescribed duly observed, its removal is proceeded with in the manner directed. Where it is found to be of lai'ge size, and the extraction of it by this method impracticable, the animal must be cast and placed under the influence of chloroform. . By this means the sphincter vesica will be relaxed and its dilation more effectually accomplished. Should the stone be too large to be removed entire, it may be crushed and extracted piecemeal in accordance with the rules already laid down. A thick, pasty, yellow deposit of calcic carbonate is occasionally found in the bladder of the male and female as the result of atony or paralysis of its walls. In l30th instances it may be readil}' removed by means of the scoop, aided by forcible injections of tepid water driven tlirough the dilated urethra. After the whole has been evacuated, an attempt should be made to restore tone to the vesical walls by repeated injection of cold water, supplemented by the administration of nerve tonics and good living. General Considerations on the Structure and Formation of Calculi. — Vesical calculi are usually ovoid in form, with their surfeces sometimes slightly and unequally flat- tened. If they have been enclosed, or partly enclosed, in a pouch or oft'- shoot from the bladder, they may be round, oblong, irregular, or dumb-bell shaped. The majority are of a dark- brown hue ; some are palish - gray, others yellowish - brown, and a few whitish-gray. All, with rare exceia- ° -^ ' ^ Fig. 162.— Vesical Calculus tions, present a rough asperous surface (fig. 162), usually more marked on one side than the other. The side on which the stone rests while in the bladder is smoother, denser, and less rounded than the other surface. In some the asperities are coarse and rounded, and impart to the stone a distinct mulberry character, but in the majority they are finer, closer set, and less prominent. In density calculi vary very considerably in different specimens, and also in difiereut parts of the same specimen, but it is rare to find them of that flinty hardness which characterizes some examples of vesicular calculus in man. In many instances they present an open spongy texture and are dis- tinguished by marked Inittleness and want of cohesion. As a rule the 370 HEALTH AND DISEASE inner portion of the stone is the more hard and compact, while the outer portion is less consistent, and, in some instances, so soft as to be readily broken down with the fingers into small rounded or angular fragments. To examine the structure of these formations the stone should be first cut with a saw and the divided surface rubbed even and smooth on a wet stone. If the polished face be now examined it will be seen to present certain structural mark- ings, of which the following are the more common examples: — 1. A regular series of closely -arranged concentric rings (fig. 163), representing sec- tions of a succession of layers of earthy matter. Of these some are narrow, some broad, some yellow or pale brown, and we gather, by the use of the knife, that they are soft or hard according as they have been In this variety the stone, as a whole, is Fig. 163. —Suction of Vesical Calculus quickly or slowly deposited. usually hard and its texture compact. 2. The laminse are irregular and incomplete, sometimes interrupted by small sinuous cavities or irregular spaces containing free earthy granules and epithelial debris. 3. Sectional surface irregular, and marked by sinuous fissures (fig. 164). Centre excavated and enclosed by a narrow strong band, from Fig. 164. — Section of Vesical Calculus Fig. 165. —Section of Vesical Calculus which arborescent rays proceed to the circumference and terminate in asperities on the surface, giving to the section a rough, coarse appearance. 4. Small groups of concentric rings forming rounded, solid - looking bodies varying from the size of a hemp-seed to that of a bean (fig. 165). They are separated from each other by a structureless mass of earthy matter, usually of less density than themselves, and in which fissures and cavities are sometimes met with. This variety consists of a number Pl-ATI- XXX Renal Calculus. Kidney of Horse CALCULI INVERSION OF THE BLADDER 371 of small laminated calculi, aggregated together and enclosed in an amor- phous deposit. All vesical calculi do not originate in the bladder. Some no doubt have their beginning in the pelvis of the kidney, in which position we have repeatedly found them in their rudimentary condition. Many of these renal formations, on reaching the bladder, are ejected with the urine, but occasionally such as acquire large dimensions are retained in the vesical cavity and undergo enlargement by earthy incrustation. It is certain, however, that stone formation is not always the direct outcome of the conditions indicated above. Foreign substances, we are aware, sometimes find their way into the bladder of the horse, notwith- standing the seeming difficulty of such an event. Some years ago Mr. William Hunting, of London, brought to the notice of the Central Veterinary Medical Society such a case, where a piece of stick, some four or five inches in length, and as thick as the little finger, was found stretch- ing across the bladder of a horse, with one end projecting through its walls into the pelvic cavity. It had evidently occupied this position some considerable time, as a large calculus had formed around its central portion. Whence the stick had come there was no direct evidence to show, and we are left to assume its possible introduction through the abdominal walls or through the alimentary canal. Such an accident as that first referred to is quite possible, but for many considerations does not recommend itself to our acceptance. From facts which have recently come to light in the human subject, we are more disposed to accept the explanation which refers its entrance into the bladder through the medium of the alimentary canal. INVERSION OF THE BLADDER The bladder of the mare may be turned inside out by spasmodic contraction of its walls, when it may be said to evert itself. The mucous membrane will then be on the outside. The accident is of very rare occurrence, and is usually brought about by the pains of parturition. It may, however, result from other causes where violent straining is excited, and the contents of the abdomen are forcibly pressed against the bladder at a time when possibly the opening into it is abnormally dilated. Symptoms. — A fleshy-looking mass, more or less rounded, projects through the vulva, varying in appearance according as the accident is recent or of some duration ; at first it is a pale pinkish-red hue, darkening with exposure to a bluish or blackish red colour. The protruding organ has been mistaken for the foetal envelopes, and fatally injured by an 372 HEALTH AND DISEASE attempt to remove them. Tlie orifiees of the ureters, by whicli the urine enters the bladder, may be found when carefully sought on the upper and anterior part of the protruding viscus, and these will set at rest any doubt as to the nature of the tumour. When labour pains are excited, little jets of urine are seen in some instances .spurting out of them from the upper part of the extruded organ (fig. 166). Without inversion the bladder may escape through a rupture in the vaginal wall, and continue to rill with urine, which, being unable to escape through the usual channel, rapidly adds to the bulk of the tumour and to the difficulty of its replacement. The muscular layer alone of the Fie Ififl.— Inversion of the Bladder vaginal wall may be ruptured, and in such case the bladder will be felt through the mucous membrane. Treatment. — Before making any examination of the extruded organ, our hands and implements should l)e rendered a.septic. Having dressed the bladder, we pi-oceed with gentle but continuous force to push it back into the vagina, seeking there for the meatus upon the floor of the passage, and gradually directing it into place with the fingers or by means of the smooth rounded end of a short stick, which should be first freely dressed with carbolized oil. The congestion and tumefaction which result from long exposure render the task of replacement more difficult, and the greatest caution will be required in manipulating the viscus le.st the swollen and softened mucous membrane be torn. It may be needful to reduce the congestion by the application of warm flannels before re]iositi()n is attempted. The THE NERVOUS SYSTEM 373 restlessness of the patient and foit'el'ul labour pains are the chief obstacles to a return of the viscus, and some restraint must be exercised to suppress them. The use of cocaine in a four per cent solution has been found helpful in producing more or less local anaesthesia, and removing the dis- position to renewed expulsive efforts which the presence of the operator's hand induces. Subsequent treatment consists in keeping the animal on soft diet and under good hygienic conditions, and the administration of anodyne medicines if pain is experienced. If a subject of this accident is again bred from, increased risk attends parturition. 4. THE I^ERVOUS SYSTEM The possession of a nervous .system is not essential to life, since in the whole vegetable kingdom, as well as in the lower animal organizations, multitudes of living forms are to be seen, which, although unprovided wdth nerves, are yet perfectly capable of preserving their independence and of holdingr their own in the struggle for existence; but wherever it is found, owing to its wonderful sensitiveness to impressions, it fulfils the important purposes of bringing the animal into relation with the outer world, of enabling it to respond to those impressions by inducing muscular movements which effect either local or general change of place or form, and finally of linking together, as with a subtle net-work, the most remote organs of the body, enabling each part to co-operate with the rest for the general good, and uniting or integrating them into a common whole. Originally the nervous system is composed of a soft living mobile substance, termed " protoplasm", from which all parts of the body are formed; and it is only by degrees that it acquires its special endowment, that of generating nerve energy, which, like other forms of force, is subject to laws of its own, and can either be stored up, liberated, intensified, or exhau.sted under appropriate conditions. In the horse, as in all the higher animals, the nervous system presents two parts for examination, one of which, and by far the larger, is named the cerebro-spinal, the other the sympathetic system. The cerebro-spinal system is adapted to respond to various kinds of impressions made upon the organs of sense, as the eye, ear, skin, tongue, and nose, to conduct those impressions through cords, which are termed nerves, to central organs represented by the spinal cord, medulla oblon- 374 HEALTH AND DISEASE gata, cerebellum, and braiu, giving rise in the first instance to responsive movements of protection or defence, and then successively, as they aftect higher and higher centres, to sensations of sight, hearing, touch, taste, and smell, and finally to ideas, emotions, and intellectual operations. The sensory impressions or stimuli thus carried to the nerve centres may not be followed by any visible effect, but in most instances, especially in animals, impulses, which we may conceive to be waves or rapidly- propagated chemical or molecular changes, start, or are liberated from the centres, which travel along similarly constituted cords or nerves, and are conducted to muscles or to glands, exciting the former to contraction and the latter to secretion. The cords con- ducting impressions from the organs of sense to the centres are named " afferent" nerves, whilst those which transmit impulses from the centres to the muscles and glands are termed " efferent" nerves. The terms " sen- sory", "motor", and "secretory" nerves are, however, most commonly used. The sympathetic system of nerves, sometimes named the nervous system of organic life, is destined to regulate the supply of blood to each organ of the body in accordance with its requirements, keeping the blood-vessels contracted when the organ is at rest, but permitting them to dilate under the influence of other nerves when in it is the active discharge of its functions. Thus in the fasting state the stomach is pale and quiescent, but in full digestion it is rosy, and performs active movements. The sympathetic system thus, by its action on the vascular system, in- directly but powerfully influences movement and secretion. It is composed of a series of knots or swellings, termed " ganglia ", united to one another by nerve cords. The more important ganglia form a chain lying on either side of the spinal column, and extending through nearly its whole length (fig. 168). Other ganglia belonging to this system, termed "collateral ganglia ", are widely distributed in the body, and give off branches which accompany the blood-vessels, and finally enter the muscular tissue in their walls. The two systems of cerebro- spinal and sympathetic ner\-es have intimate relations with each other. Their structure is very similar. The sympathetic system consists of numerous nerve cords and ganglia distributed over the body, and destined to control and regulate the organs Fig. 167.— Ganglion Cells of the Sym- pathetic Xerve of the Muscular Coat of the Bladder (magnified about 350 times) a, a, a, Ganglion Cells. Nuclei, c, c, c, Axis Fibres. Fibres. I, h. Their rf, rf, Spiral THE NKKVOUS SYSTEM 375 of \ogetative life. Tlie m;iiii trunks of this system are two in number, one running on either side of tiie verteliral column, extending from the head backward as far as the tail. Each in its course has upon it a number of small round or ovoid bodies termed ganglia. These consist of a covering of connective tissue, from which small septa pass into the interior. The spaces thus formed in the organs are filled in with small cells, some of which are round, while others have proceeding from them small fibres or poles, by which -^ / Fig. 168. — Diagram of the Ganglia of the Sympathetic System of Neires ' Superior Cervical Ganglion. -, - Cervical Sympathetic Cord. ' Middle Cervical Ganglion. * Inferior Cervical Ganglion. * Cerrical Portion of Sympathetic. ^, ^ Dorsal Sympathetic. ' Lumbar Portion of Sympathetic. * Sacral Portion of Sympathetic. ' Great Splanchnic Nerve. '" Lesser Splanchnic Nerve. " Solar Ganglion. '= Afferent Branches from Spinal Pairs. " Peh-ic Plexus. '♦ Branch to Pelvic Plexus. '^ Spermatic Plexus. '^ Posterior Mesenteric Plexus. '" Branches from Posterior to Anterior Mesenteric Plexus. '^ Lumbo-Aortic Plexus. '" Superior CEsophageal Branch. '" Inferior (Esophageal Branch. -' Cardiac Nerves. ^ Branch to Pelvic Plexus. ^ Conjoined Cord of Pneumogastric and Sympathetic Nerves. they are connected with nerve -tubes, w^hich go to (afferent) and come from the ganglia (efferent). Some nerve -fibres also pass through the ganglia, and in doing so are brought into contact w^ith the cells. As the sympathetic chain runs along the side of the vertebrae, a small ganglion appears upon it, opposite to each intervertebral gap or hole, out of which the spinal nerves emerge. The .spinal nerves on passing out of the spinal canal divide into an upper and a lower branch, and from each of the latter a few fibres proceed to the sympathetic ganglia and reinforce the sympathetic chain. The different parts of the sympathetic cord are distinguished by terms indicating the region wnth which they are connected, hence the terms cervical or neck, the dorsal or back, the lumbar or loin, and the sacral or croup plexuses or nerves. 376 HEALTH AND DISEASE Cervical Sympathetic. — The cervical sympathetic consists of two large ganglia united, by an intervening cord. The ganglia are distin- guished as the superior and the inferior cervical. Sometimes there are three. The superior cervical ganglion, situated beneath the atlas, gives branches to those nerves in its vicinity — ■ the glosso-pharyngeal, spinal accessory, pneumogastric and hypoglossal, and the lower branch of the first cervical nerve. The eflerent branches, or those which jjass from the ganglion, are fila- ments to the internal carotid artery, others to the three divisions of the common carotid, and to the guttural pouch and pharynx. The branches which accompau}' the internal carotid into the cranium form the cart)tid and cavernous plexuses, and are connected with the fifth cranial nerve. The sympathetic cervical cord passes down the neck in company with the pneumogastric, which it leaves on entering the chest and joins the inferior cervical ganglion. In its course down the neck no filaments are received or given off by it. The Inferior Cervical Ganglion.— As we have already pointed out, this is sometimes double, the t\\ o being joined together by a short grayish band. When this condition exists, the portion in front, which is always the smaller, is known as the middle cervical ganglion. The afferent branches, or those which go to the ganglion, are two in number, one resulting from the union of small filaments from the second, third, fourth, fifth, sixth, and seventh pairs of cervical nerves, and the other derived from the eighth cervical nerve. The efferent branches of the inferior cervical ganglion are mainly dis- tributed to the heart. Some very fine filaments may also be seen to enter the anterior mediastinum, or proceed to the branches of the brachial trunk. The Dorsal Sympathetic Chain. — When the inferior cervical ganglion has given 1 tranches to the lieart, the dorsal sympathetic chain is continued on from it in a backward direction, between the costo- vertebral articu- lation and the jjleura. As it passes backwards there appears upon it a number of very small ganglia, one of which is situated against each of the vertebral openings through which ^lass the spinal nerves. Each ganglion receives one or two small afferent filaments from the inferior branches of those nerves. In its course backwards it gives off the great splanchnic nerve at a point corresponding to the seventh intercostal space. From this point it proceeds backwards, and in its course receives a small Inanch from each of the sranoflia. THE NERVOUS SYSTEM 377 It then proceeds to the side of the aorta between the ceeliac axis and the large mesenteric artery, where it has upon it the semilunar or solar ganglion. This is a body of considerable size and importance. It is joined to its fellow on the opposite side by a large wide branch and numerous smaller ones, resulting in the formation of a plexus beneath the aorta termed the sokn' j)le.ru^. After receiving some branches from the pneumogastric nerve, this plexus splits up into several smaller plexuses, which form a net-work round the arteries, and through them the sympathetic is distributed to the several abdominal organs. In this way we get the gastric plexus to the stomach, the hepatic plexus to the liver, duodenum, pylorus, and pancreas, a splenic plexus to the spleen, and also a plexus to the stomach. A large plexus, the anterior mesenteric, surrounds the artery of that name, and is dis- tributed over the organs supplied by it. A renal plexus encircles the renal artery and accompanies it to the kidney. The lumbo-aortic plexus passes backward along the under surface of the aorta, and mixes its fibres with the posterior mesenteric plexus. The great splanchnic nerve leaves the dorsal chain about the seventh intercostal space. From this point it receives a few afferent fibres from the ganglia, commencing with the sixth, and continues to do so irregu- larly up to the sixteenth. Behind, the great splanchnic ends in the solar plexus. The lesser splanchnic nerve is made up of two or three small branches proceeding from the last dorsal ganglion; these collect into a short thin branch, which joins the solar plexus or the renal and supra- renal plexuses. Lumbar Sympathetic. — This is a continuation of the dorsal sym- pathetic, and has upon it ganglia corresponding to the number of lumbar nerves fi'om the inferior division of which it receives its afferent branches. Behind, it is continued by the sacral sympathetic. Its efferent branches consist of short filaments to the lumbo-aortic plexus. The small mesenteric artery receives others, which surround the vessel and form the posterior mesenteric plexus, in the centre of which is a ganglion of some size. This ganglion supplies in addition branches to the posterior mesenteric vein, and others to the spermatic arteries and the rectum. Two or three long divisions from each side pass beneath the peritoneum, and on reaching the lateral part of the rectum blend with others from the inferior sacral nerves, forming the plexus from which all the pelvic organs are supplied. Sacral Sympathetic. — This region is supplied by a continuation 378 HEALTH AND DISEASE backwards of the lumbar division. It presents four long ganglia, which communicate with the inferior sacral nerves by a few small filaments. This plexus distributes its branches to the coccygeal artery, and in a somewhat iiTegular manner to other neighbouring parts. Structure of the Cerebro-spinal Nervous System. — If a fragment of the brain or spinal cord be examined with the unassisted eye, it appears to be composed of a soft curd-like material with red points and streaks distributed irregularly through it, differing a little in colour in different parts, being here almost pure white and there pinkish gray, but every- where so soft and apparently destitute of structure, that Haller, one of the most learned and expert physiologists of the eighteenth century, could only describe it as a uniform pulp with but few indications of structure, presenting only blood-vessels and some ol)scure fibrous markings. The great improvements that have been made in the construction of the microsco^je, and in the process of hardening, cutting, staining, and mount- ing specimens for microscopic examination, now enable it to be shown that whilst there is an abundant supply of blood circulating through each part, the essential elements of every nervous system are neTve-cells and nerve-flhres, both of which require careful consideration. ^■^•^ts Fig. 169.— Nerve-Cells Fig. 170.— Nerve-Cell A, Nerve-Cell. B, Axis-Cylinder Process, uniting with c, a Nerve. The Nerve-cells. — The nerve-cells are bodies of rounded, oval, or irregular form, varj'ing greatly in size, but always microscopic, and having an average diameter of about 1 -2000th of an inch. Each cell contains in its interior a small but important structure, named the " nucleus", lying in a mass of finely fibrillated protoplasm, and itself containing a still THK NERVOUS SYSTEM 379 sniiiUer particle, named the " nucleolus". The surface of the nerve-cell is sometimes smooth, and gives off one or two fine filamentous processes; in some instances, however, many such processes shoot from it. These divide and subdivide as they recede from the cell, and either join with or enter into very close relation with the processes from other cells. In most, if not in all cases, one of the processes is larger and longer than the rest. If traced for some distance it may be seen to become a true nerve -fibre, which may terminate in a muscle or in a gland, or in one of the organs of sense — ear, eye, nose, &c. — or may serve to bring two nerve-cells into connection with each other. The Nerve-fibres. — Nerve-fibres are processes or outrunners from the cells. At the point where a fibre springs from a cell it is exceedingly fragile and delicate, but as it travels away from the cell it gradually acquires a protective covering or sheath, which calls to mind that employed to insulate a telegraph wire. It loses it, however, again as it approximates its destination, becoming reduced to a very attenuated thread. If exaniined in the middle of its course, say, for example, in the sciatic nerve, each fibre will be found to consist of a central core or axis cylinder, believed to be the path along which all nervous impressions and impulses are propagated. Covering this is a layer of white substance of a fatty nature, named the medullary sheath, or white substance of Schwann, and outside this again is a delicate but firm and resistant membrane, which is the neurilemma; such nerve-fibres are named " meduUated fibres". The central core or cylinder axis often runs for long distances without division, but at times gives off collateral branches, and may even divide into a set of branches like a bouquet. MeduUated fibres vary in diameter from 1- 1500th to _ 1- 12,000th of an inch. The fibres are bound together "of Nerve into bundles by connective tissue, and these bundles are a, Nerve-Fibre. associated into groups, the whole having a strong invest- ^ Neurilemma''***'^ ment of connective tissue and constituting a nerve. The results of injury to the central parts of the nervous system are so disastrous that they are everywhere protected from mechanical violence with the greatest care. The spinal cord, cerebellum, and brain are con- tained in a strong case of bone particularly well adapted to preserve these soft parts from blows or pressure. The head bones are composed of an outer and an inner layer of compact bone, between which is a layer of loose cancellous or spongy bone, the whole requiring great force to cause fracture, whilst the solid bodies and projecting spines of the backbone, together with the successive layers of thick skin, fibrous tissue, and muscles 380 HEALTH AND DISEASE that cover it, are equally competent to protect the spinal cord. The skull will not indeed resist the penetrating power of a bullet, nor will the spine resist the weight and shock of a heavy rider in leaping into a ravine, but they will preserve the nerve centres intact through all the ordinary casualties of life. The bones are not the only means of guarding these parts from injury, for the osseous case is lined by a thick and extremely tough membrane, the dura mater, thin sheets of which dip down between the two hemispheres of the cerebrum, and between the cerebrum and cerebellum, and prevent the former from unduly pressing upon the latter. Within the dura mater is a thin double membrane, named the arachnoid, one part covering the inside of the dura mater and the other the outer part of the brain. These two op- posed surfaces are lubricated with a serous fluid, which permits a slight gliding movement of the brain, such as accompanies the act of breathing and the beating of the arteries, with the least possible friction. And lastly, the whole surface of the brain is immediately invested with the jna mater, which is a membrane of blood-vessels, the branches being so numerous and so closely arranged in it that it may almost be said the great nerve centres rest in every position of the body on a fluid bed. The nerve centres and the nerves receive an abundant supply of blood. The branches of the internal carotid artery and those of the vertebral arteries are distributed to the brain and cerebellum, whilst the .spinal cord receives blood-vessels from the vertebral arteries, which run down the upper and lower surfaces of the cord as the spinal arteries, and are rein- forced as they descend by many branches from the intercostals and posterior aorta. The blood thus distributed is returned from the head and spine by the jugular and spinal veins. The nerves of the trunk and extremities receive their blood from the nearest artery, and return it to the neai-est vein. The Spinal Cord. — The spinal cord or spinal marrow is a long, nearly cylindrical mass of nerve substance which extends from the head to the sacral region of the spine, and weighs about 10 ozs. It is contained in a canal formed by the successive vertebrte, which is wider than itself, so that there is no danger of any pressure being exerted upon it in the various movements the body is capable of performing. It has the same coverings as the brain, which are named dura mater, arachnoid, and pia mater. In front the cord enlarges both in breadth and thickness, and is continuous with the brain through the medulla oblongata. Behind it terminates near the anterior third of the sacral region. It does not preserve the same diameter from one end to the other, but presents two THE NERVOUS SYSTEM 381 ^2fe: swellings, one extending from the fifth vertebra of the neck to the fourth vertebra of the back, and the other situated in the region of the loius. These enlargements of the nervous mass are ren- dered necessary in order to supply the great nerves distributed to the fore and hind limbs respectively. The spinal cord gives origin in the horse to forty- two or forty-three pairs of nerves, each of which arises by two roots, a superior and an inferior. The position and arrangement of the successive pairs are shown in the accompanying diagram. If the cord be divided transversely the apjjear- ance presented in fig. 173 will be seen. The shaded area is named the gray substance, the light area the white substance, of the cord. The white substance is composed almost exclusively of nerve-fibres; the gray substance, whilst contain- ing many fibres, presents also a large number of nerve-cells. The cord is seen to be divided into symmetrical lateral halves by two fissures, the superior fissure being narrow and deep, and the inferior \vide and more shallow. The gray sub- stance of the cord somewhat resembles the letter H, or a jDair of inverted commas, placed back to back and united l>v a cross bar. The extremities ^:^ 13 SB. M'!l'i'^^"■■^' Fig. 173.— Sections of Spinal Cord ' Superior Root. - Inferior Koot. ' Ganglion. * Superior Nerve. ^ inferior Nerve. « Choroid Plexus. ' Nerve Substance. 8, 1" Inferior Comua. » Superior Cornu. " Central Canal. " Superior Longitudinal Fissure. " Inferior Longitudinal Kiiisure. 382 HEALTH AND DISEASE of the comma - like bodies are named the coruu, aud thure are conse- quently an upper and a lower cornu on each side. The upper one is more pointed, and reaches nearer to the surface than the lower cornu. The isthmus or central portion, which joins the two lateral masses of gray substance, is perforated by a small hole, which rejjresents the section of a tube, named the central canal, which runs the whole length of the cord. If the nerve roots be traced into the substance of the cord, it will be found that the fibres of which they are composed chiefly end in branches surrounding the nerve-cells of the superior and inferior cornu of their own side, whilst some ascend towards the brain on that side, and others cross over to the opposite side. Each half of the white substance of the cord is obviously divided into three regions: 1, an upper, between the superior cornu and the superior median fissure; 2, a lateral, between the upper and lower cornu; and 3, a lower region, between the inferior cornu and the inferior median fissure. In some instances the fibres constituting these divisions con duct impressions forwards, in others backwards. Some are chiefiy made up of sensory nerves, Fig. 174. — Under Surface of Horse's Brain A, Temporal Lobe. B, Crura Cerebri. c, Pons Varolii. D, Medulla Oblongata. B, Cerebellum. F, F, Convolutions of Cerebrum. I, Olfactory Nerve or 1st Nerve. n, Optic Nerve or 2nd Nerve. Ill, Motores Occulorum or 3rd Nerve. iv, Pathetici or 4th Nerve. V, Trifacial or 5th Nerve, vi. Abducent Nerve, vn, Facial or 7th Nerve. viii, Auditory or 8th Nerve. IX, Glosso- pharyngeal or 9th Nerve. X, Pneumogastric or 10th whilst OthcrS are CSSeutially motOf. Nerve. xi. Spinal Accessory or 11th Nerve. xu. Hypo- /-», i • • t ^ glossal or 12th Nerve. Uthcrs again are mixed, and con- vey impulses both upwards to the medulla oblongata, cerebrum, and cerebellum, and downwards from these centres to the muscles. The Bulb, or Medulla Oblongata. — This portion of the nervous system (d, fig. 174) occupies a position intermediate between the spinal cord and the pons (o, fig. 174), and is continuous with both. It forms a kind of capital to the cord, and possesses a highly intricate structure. It is the seat of origin of some of the most important nerves in the body, particularly of those which confer sensibility upon the face and THE NERVOUS SYSTEM 383 head, which perceive sounds, and which are instrumental in carrying on the function of breathing, and as these last ai-e essential to life, destrurtinn of the medulla oblongata is immediately fatal. The Pons (c, tig. 174) is a broad and thick band of transverse fibres running across from one hemisphere of the cerebellum to the other. It is traversed by the continuation of the columns of the spinal cord. These emerge from the front border of the pons, and form the diverg- ing crura cerebri (b, fig. 174), the fibres of which radiate outwards to the cortex of the brain. Effusions of blood affecting these columns cause paralysis. Above the pons are the four eminences named the corpora quadri- gemina, which are intimately connected with the function of sight, and are seen in section just above N in fig. 176. We now reach the great ganglionic masses situated at the base of the brain, shown in fig. 175. These are large, and composed of gray substance, and therefore contain many cells, in which it is probable many of the nerve-fibres in the crura cerebri end, whilst on the other hand they are brought into relation with the cortex of the brain by radiating fibres. The hinder pair are the optic thalami, and are closely connected with the optic tracts. The front pair are the corpora striata, so termed because the gray substance is traversed by bands of white fibres. These great ganglia are connected by transverse fibres forming the gray and white commissures, and the rest of their opposed surfaces form the lateral boundaries of the third ventricle. The Brain. — The large mass of nervous substance which fills the cavity of the cranium or skull, to which the term brain is ordinarily applied, in reality consists of two parts — the cerebrum or brain proper, and the cerebellum or little brain, the proportion of these organs to each other by weight being about as 7:1. Both together weigh in the horse about one pound and a half, which, as compared with the weight of the body, is about as 1 : 600, or about 26 grains for each 1 lb. av. of body weight. The Cerehr^im, or brain proper, is divided by a deep fissure running from before backwards into two lateral halves. It consists of an immense but thin sheet of gray nerve substance externally, chiefly composed of nerve-cells, and internally of a mass of white substance composed of fibres proceeding from, or running to, the cells of the gray substance. Externally the brain is covered by three protective membranes, as well as by the bones of the skull and skin. These three membranes are the pia mater, which is closely attached to the brain, and is composed 384 HEALTH AND DISEASE principally of blood-vessels; the arachnoid, which is a serous mem- brane, and is uext outwardly placed; and the dura mater, which is a tough fibrous membrane, and lines the interior of the skull. The outer layer of gray ner\e substance being very much larger than the surface of the brain, is folded, and, as it were, crumpled, and made to dip down some distance into the organ. The folds are named con- volutions (fig. 175 a), and the depressions or grooves between them sulci (fig. 175 b). The convolutions appear at first sight to l)e quite irregu- larly disposed, nor will their arrangement be found exactly the same in any two lirains; yet by tracing their develop- ment, and by observing the eftects of injuries, a general similarity has been demon- strated in their position, and the function of each has become pretty well known. If the brain be sliced hori- zontally a little below the le^'el of the corpus callosum, a cavity is opened on each side named the lateral ventricle. These two ventricles are separated by the septum lucidum, but com- municate with each other an- teriorly, and with the third ventricle by the foramen of Monro. The floor of each lateral ventricle is formed by the corpus striatum in front, and the optic thalamus behind, and upon these lie numei-ous blood-vessels forming the velum interpositum and choroid plexus. The third Aentricle is situated between the two corpora striata and optic thalami, and is crossed l)y a gray and two white com- missures. Behind, it ends in the aqueductus sylvii, which is a tunnel running underneath the corpora quadrigemina and pons, and opening behind into the fourth ventricle, which is again continuous with the central canal of the spinal cord. The cerebellum is situated behind the brain and aliove the medulla oblongata. Its convolutions are more numerous than those of the brain, but present the same crumpled disposition of the gray and white sul)- MEDULLA OBLONGATA Fig. 175. — Upper Surface .anrl Horizont.al Section of the Brain A, Ai, Convolutions. B, Bi. Sulci, c, CJray Matter. D, White Matter. COR. sTB., Corpus Striatum. OPT. thal. , Optic Thalamus. THE NERVOUS SYSTEM 385 stance, the gray forming the external hiyer and tlie white tlie inteinal. The tree-like appearance presented when the cerehellum is cut in half lias been termed the arbor vitce. The cerebellum is divided into two hemispheres, and a central portion named the vermiform process. At its base the white fibres forming its fibrous substance are gathered together into three great strands, groups, or peduncles, on each side; the lowest or most posterior connects it with the lateral columns of the spinal cord. The middle group forms a great part of the pons, and crosses to tlie ? ; i i ; 1 ' f opposite hemisphere, while the third group runs forward to the cerebrum. We have seen that forty - two "or forty -three pairs of nerves arise from the spinal cord. Twelve more pairs arise from the brain and parts within the cranium, and are termed cere- bral nerves. From the importance of the parts the latter supply they have received distinctive names, and appear in the following order: — 1. Olfactory, or nerve of smell. 2. Optic, nerve of sight. 3. Motores oculi, nerve of motion to the muscles of the eye. 4. Pathetici, distributed to the superior oblique muscle of the eye. 5. Sensory motor nerve, supplying the skin of the head and face with sensation, and the muscles of mastication with motor nei-ves. 6. Abdu- centes, supplying the external rectus or straight mu.scle of the eye. 7. Facial, supplving the muscles of expression in the face. 8. Auditory, the nerves of hearing. 9. The glosso-pharyngeal, supplying the nerves of taste and some of the muscles ministering to the act of swallowing. 10. The vagus, which supplies the pharynx and larynx, the trachea and oesophagus, the lungs and heart, and the liver and other vi-scera with fibres, some of which are motor, while others are sensory. 11. Spinal Fig. 176. — Longitudinal Section of the Bi.iin A, Cerebral Convolutions. B, Section of the Corpus Callosum. c. Section of the Fornix. D, Septum Lucidum. E, Internal Extremity of the Hippo- campus. F, Vena Plena conveying Blood from the Choroid Plexus and Velum Interpositum. G, Pineal Gland divided. H, Gray Commissure. I, Anterior White Commissure. J, Corpus Albicans divided. K, Section of Optic Chiasraa or Optic Decussation. L, Pituitary Gland. M, Medulla Oblongata in Section. N, Valve of Vieussens in Section. o, Aqueduct of Sylvius. P, Section of Cerebellum. Q, Fourth Ventricle. R. Section of Pons Varolii. s. Section of Crura Cerebri. T, Foramen of Monro. u, Olfactory Lobule from whence spring the Olfactory Nerves. 386 HEALTH AND DISEASE accessory, supplying some of the muscles of the neck and shoulder. 12. The hypoglossal, supplying the muscles of the tongue. The Functions of the Nervous System. — Having thus acquired some knowledge of the anatomical and microscopical characters of the nervous system, we may proceed to consider the purposes it fulfils in the l)ody. Of the two constituents of the nervous system, cells and fibres, the cells are regarded as the organs by means of which impres- sions are perceived and registered, and impulses to motion or secretion generated, whilst the fibres are mere conductors extending between the cells and the particular tissues to which the nerve-fibres issuing from the cells are distributed. Those nerves which conduct impressions from one or other of the organs of sense — eye, ear, mouth, nose, skin, &c. — to the s^jinal cord or brain are called sensory or afierent fibres. Those which conduct impulses from the cord or brain to the muscles or glands are named "efferent" or "motor" nerves. The rapidity with which the conduction of impressions or impulses is eflected is very considerable. It is obvious that if the knowledge of the proximity of food or of danger, communicated by the senses, which are the outposts of the nervous .system, is to prove of service, it is necessary that the information should be both accurate and prompt. The accuracy is provided for by the special attributes of the several senses. By daylight, the eye affords most of the information required, though in the majority of animals the ears are constantly on the alert against the approach of an invidious foe. At night the faculties of hearing and smell are those which are specially exercised, and in many predatory animals their acuteness rises to a height of which we can form luit a faint idea. By whichever of the senses the impressions are conveyed to the cells of the central nervous system, it is important that the muscular responses should be effected with promptitude. At first sight it might appear impossible to acquire any definite knowledge of the swiftness with which sensory impressions of objects affecting the animal, and the motor impulses by which it responds to them, are propagated. The speed of thought is proverbial, yet by the application of electrical currents, the rapidity of which may be regarded as covering short distances and intervals with no appreciable loss of time, conclusions have been arrived at showing that nervous changes, currents or waves, travel at a much slower speed than the electric current. It has been ascertained that nervous impulses, whether in an afferent or in an efferent nerve, that is, whether sensory or motor, in animals as different as a froo- and a horse or man, travel at the rate of about THE NERVOUS SYSTEM 387 a hundred feet per second, or nearly at tlie rate of twenty-two miles per hour. The most careful researches into the elements which enter into the chemical composition of nerve tissue afford no insight into the extra- ordinary properties it possesses. In the living state it may be regarded as a kind or form of protoplasm, but when dead and submitted to analysis it only presents those elements with which we are familiar in the proteids — carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus, with salts of calcium, sodium, potassium, and magnesium. Complex substances known as protagon and neurokeratin may be obtained by analysis, but these are but the caput moHuum of the active, living, sentient material, which receives impressions, retains and reproduces them, and can liberate impulses. We are yet far from being able to predict function from chemical composition or molecular arrangement. It is interesting to notice that the gray substance of the cord and brain, which by common consent is acknowledged to be the active part, contains no less than from eighty-five to ninety per cent of water, whilst the white part, chiefly composed of fibres, contains only about seventy per cent. The reaction of nervous tissue is alkaline to test-paper. Speaking generally, three parts are recognizable in every nerve-fibre: the origin, which is usually from a cell in one of the nerve centres; the course, which is longer or shorter in correspondence wdth the part of the body supplied; and the termination, which presents special modifications, in accordance with the special organ of sense to which the nerve is dis- tributed, if it be a sensory nerve, or the muscle or gland, if it be a motor nerve. The agent exciting a nerve to action is named a stimulus. Some stimuli, as electricity and mechanical irritation, seem to be able to excite all nerves to action, but, as a rule, each nerve responds, or responds best, to its own proper stimulus. Thus the undulations of light excite specifically the nerve terminations in the retina of the eye, the vibrations of sound those in the ear. The change, or information of the change, exciting the nerve endings, say, from blue to red in the case of light, is propagated along the nerve -fibre till it reaches a special sensory cell in the nerve centre. The cell, if well - nourished and not already ex- hausted, is excited, and a wave of force is liberated from it which may be propagated to a neighbouring cell, and may expand itself through it in producing ideas, or movement, or secretion. The stimuli with which we are most familiar, besides those of electricity, light, and sound already mentioned, are those of contact or of a mechanical nature, those of a chemical nature, as odours and tastes, those of temperature, and those 388 HEALTH AND DISEASE proceeding from the exercise of the will. The last always originate within the nerve centre, and the impulses they awaken travel from that centre and expend themselves on muscles or glands. It is possible that some animals may have nerves capable of responding to stimuli of which we have no more conception than a man born blind has of light, as they certainly have nerves which recognize variations in the intensity of ordinary stimuli that are imperceptilile to us. Thus the presence of water, or the proximity of one of their own species, is recognized by many animals when quite imperceptible to man. A stimulus may be so feeble that it fails to be propagated to the central nerve-cells, and is then said to be insufficient or inoperative ; but though our application of the stimulus may not be thus propagated with such intensity as to excite the cell to dis- charge itself, it may awaken its activity if frequently repeated, and cause it to respond, just as a touch which fails to awaken a sleeper, will do so if repeated. This constitutes the summation of a stimulus. The chemical stimuli are represented by the various mineral and vegetable acids, bv alkalis, by ethereal and alcoholic liquids. As a rule, any chemical sub- stance that produces sensation when applied to a sensory nerve, will cause contraction of muscle when applied to a motor nerve, but experiment has shown that the motor nerves are more strongly affected than the sensory by alkaline solutions. The spinal cord is primarily to be regarded as formed by the union or joining together of many nerve centres, that is to say, of many groujjs of cells, which commonly act together or in an orderly sequence, producing purposive actions, without any voluntary effort, beyond perhaps supplying the first incentive or stimulus. Even this may be entirely absent, and the animal may have no consciousness of the nerve stimulus or of the muscular actions that follow it. The complete independence of a segment of the spinal cord is well shown in cases where the spinal cord has been crushed in the region of the back by a fall, or a musket-ball, or a sabre- cut. The voluntary movements of the hind limbs are abolished, the animal can neither move them nor feel any injury inflicted n^Jon them. It is said to be paralysed, yet if the skin of the limb be pinched, or touched with a hot body, it will immediately respond by kicking, or bv some other spasmodic movement of the paralysed liml). Similarly, b}- appropriate stimulation the bladder or the rectum may be made to dis- charge its contents. Such actions or movements are said to be reflex. It can be shown that a stimulus applied to the skin excites a waxe which travels up the nerve, enters the cord by the superior root of one or more of the spinal nerves, and reaches one of the nerve-cells in the superior cornu. From this it passes into the inferior cornu and reaches THE NERVOUS SYSTEM 389 one of the motor cells, aud this inimediately liberates an impulse, which, emerging by the inferior root, travels down the motor nerve to the muscle. As many sensory nerves are always stimulated, many motor nerves are called into action, and these are so connected and associated together as to produce purposive movements. In the illustration just given, the retlex movements are said to be icitliout conscio^lsness, and they are analogous to those that are constantly taking place in the uninjured animal in the movements of the intestine, of the heart and blood-vessels, of respiration, and of the ducts of glands; but in a large number of cases reflex acts are accompanied by consciousness, as in the case of winking when the eyelashes are touched or the eye is exposed to a bright light, or of coughing or vomiting fi-om tickling the throat with a feather, or of micturition from over-distension of the bladder. When the animal desires to perform one of these purposive and complex movements, it does not transmit a separate impulse to the several muscles implicated in the act, for it knows nothing of them, but by an act of the mind it transmits a mandate to a group of cells which have learned to act together in a definite order and to produce the retmired efiect. Such centres are named co-ordinating centres or nuclei, and of these there are many, as, for example, those governing the movements of the rectum and bladder in the acts of discharging the faeces and urine; those rec|uired for parturition, and for the erection of the penis and the ejaculation of semen, which are chiefly situated in the lumbar and sacral regions of the cord; and finally,, tlie contraction of the blood-vessels of the abdomen and lower limbs, which are chiefly situated in the dorsal region. There appears also to be present in the cord, centres that control the production of animal heat and of the secretion of sweat, these effects being in part due in both instances to changes in the size of the blood-vessels, and in the case of the sweat secretion to direct action of the nerves on the sweat glands. We must regard the cord as endowed to an eminent degree with im- pressionability; and the power of inducing reflex acts wdthout consciousness. But the cord is not a receiver of nervous impressions and a generator of nerve impulses only; it is also a conductor transmitting impressions made upon the skin to the medulla oblongata, cerebellum, and cerebrum on the one hand, and impulses originating in these parts to the muscles of the limbs and trunk, and to the other organs of the body. The medulla oblongata, while it is a prolongation upwards of the spinal cord, and transmits impressions both from the cord to the brain and cere- bellum, and downwards from these parts to the cord, is also itself a very important centre, containing many groups of cells which preside over and 3'JO HEALTH AND DISEASE govern the complex muscular movements of mastication, insalivation, deglutition, winking, breathing, with its accessory movements of coughing and sneezing. The corpora striata and optic thalami, or great ganglia, at the l)ase of the brain, are probably the regions where consciousness first appears, con- sciousness of the different forms and kinds of nervous stimuli, and the place where conscious efforts or muscular movements are made in response to them. These ganglia are particularly connected with the sense of sight. They are relatively large in the horse, for whilst in man their proportion to the brain may be taken as 5 : 100, in the horse it is 13 : 100. The outer layer or cortex of the brain is the highest centre of all. It is the seat of the emotions of judgment, memory, reason, and the will. We have seen that it consists of gray substance containing many nerve-cells, which give off fibres that extend to and from the ganglia below and to the periphery of the body. It has often been exposed as the result of accident, and has uniformly been found to be insensitive to direct stimulation, so tliat large portions have been cut away without pain being exjjerienced even in man. Evidence has accumulated during the past few years, show- ing that the several convolutions have definite functions, so that one set is concerned with the initiation of movements of the head and neck, another with those of the fore-limbs, and others with those of the trunk and hind- limbs. Special lobes of the brain are also connected with the several senses, the occipital lobes being especially connected with the visual sense, the temporo-sphenoidal lobes with the hearing. The horse appears to be an animal endowed with a remarkable power of association of definite movements with certain mental stimuli, and with an excellent memory. It will stop before the customers' doors, the sound of the rider's voice will cheer and direct it, and in military evolutions the bugle-calls are quite as well known by the horse as by its rider. It will remember events that are long past. It enters into the spirit of trials of speed and strength, and of games, as those of polo and steeple- chasing, with the utmost zest and enjoyment. The horse owes his proud position with the dog, as the friend of man, to his docility, his gentleness, his great muscular strength and swiftness. iSEKVKS, Airi'Klv'IKS, AND 1. Inner Deki- 1. Ailcltictoi-s. 2. ObUiratdi r.\lenius. :5. Semimembrauosus. 4. Biceps feraoris. 5. Semiteudiuosus. 6. Gastrocnemius. 7. Semimembranosus. 8. Adductor macfiius. 9. Vastus intenius. 10. Pectineus. 11. Sartorius. .MTSCLKS OK THK LI.MliS- I Asi'E( r OK Thich 12. Tc'iuluu common to proas niajj;nus ain iliacus. 13. Pectineus. A. Obturator ai tery. B. Great sciatic nerve. c. External popliteal nerve. D. External saphenous nerve. E. Femero-popliteal artery. F. Femoral artery. G. Deep femoral artery. H. Prepubic artery. 11. Inner Aspect of Fore-Limb 1. Supi-ascapular artery. 2. Circumflex nerve. 3. Ulnar nerve. 4. Roots of median nerve. 5. Axillary artery. 6. Musculo-spiial nerve. 7. Nerve to biceps. 8. Prehumeral artery. 9. Median nerve. 111. Musculo-cutaneous nerve. 11. Artery to biceps. 12. Posteiior radial artery. 13. Internal plantar nerve. 14. Anterior digital nerve. 15. Oblique l)ra,nch connecting the internal with external ])lantar nerve. 16. Internal met;\carpal vein. 17. Large metacarpal artery. 18. Small metacarpal artery. 19. Large metacarpal artery. 20. External plantar nerve. 21. Ulnar arterj'. 22. Ulnar nerve. 23. Ulnar nerve. 24. Anterior radial artery. 2.J. Ulnar artery. 26. Bracliial artery. 27. Deep humeral artery. 28. Artery to latissiuuis dorai. 29. Subscapular artery. A. Subscapularis. B. Sujiraspinatus. c, c. C'oraco-humeralis. u. Posterior deep pectoral. E. Biceps. V. Extensor metacarpi magnus. G, G. Flexor metacarpi internus. H. Extensor metacarpi obliciuus. I, I. Teres major. .1. Latis.sinuis dorsi. K. Caput magnum. L. Caput parvum. M. Radial head of flexor metacar])i inediu.s. N. Ulnar head of flexor metacarpi medius. o. Ulnaris accessorius. p. tJonjoined tendon of flexor metacarpi internus. NERVES, ARTERIES, AND MUSCLES OF THE LIMBS— 1 I. Inner Deep Aspect of Thigli. II. Inner Aspect of Fore Limb. cp:kebko-spinal nerves 391 CEREBRO-SPINAL NERVES THE CRANIAL OR ENCEPHALIC NERVES If we examine the base of the brain, a number ot ncrxcs are seen to come off from its surface. They vary in size, as the}' do also in function, and among them are numbered the nerves of the special senses of smell, sight, taste, and hearing. The cranial nerves are arranged symmetrically on either side of the base of the brain, and for the most part distribute their branches to parts on the side from which they arise. There is a want of agreement in this country between human and veterinary anatomists as to the enumeration of the cranial nerves. By the one they are described as nine, by the other as twelve. We need not, however, enter into the ]>ros and cons of this question here, but we give below the numerical tlesignations of each: — Xame. Veterinary. Human. Olfactory Ner\-es ... ... ... ... 1 1 Optic Nerves ... ... ... ... 2 2 Oculo-motor Nerves ... ... 3 3 Pathetic Ner\es ... ... ... ... 4 4 Trifacial or Lingual Nerves ... ... 5 5 Abducent Nerves ... ... ... 6 6 Facial Nerves (Portio dura) ... ... 7) -, Auditory Nerves (Portio mollis) .. . ... S) Glosso-pharj'ngeal Nerves ... ... 9^ Pneumogastric or Vagus Nerves ... ... 10 8 Spinal Accessory Nerves ... ... ... 11 J Hypoglossal Nerves ... ... ... 12 9 First Pair, Olfactory. — The first pair of cranial nerves is the olfac- tory, a number of fine filaments whose superficial origin is the olfectory Ijulbs. These bulbous bodies are lodged in the ethmoidal fossaj of the ethmoid bone, two depressions in front of the cranium, in which a number of minute openings appear and allow of their passage out of the cranium into the superior parts of the nostrils, where they are distributed over the schueiderian membrane. The olfactory nerves are the first pair of special nerves, whose function is that of receiving the impressions of odours, which the}- carry to the brain. Second Pair, Optic Nerves. — These nerves are derived from two thick bands which wind round the crura cerebri in their course from their deep origin in the corpora quadrigemina. On reaching the inferior surface of the cranium, the two optic bands 392 HEALTH AND DISEASE comhiiie to form the commissure or cliiasma of the optic nerves, which is lodged in a depression at the base of tlie cranium — the optic fossa. It is important to understand the behaviour of these nerves on reaching the commissure. To look at, it would almost seem as if the nerves pro- ceeding from the optic tracts had crossed in their course, and had gone to the eye on the side opposite to that on which they first appear before the chiasma is reached, but this is not exactly the case. As a matter of fact, the great bulk of the nerves do cross, but a certain number of filaments continue on the original side and pass into the eye on that side. We find, therefore, that fibres from the left side mingle with fibres from the right, and together form the right optic nerve, and vice versa. It should also be noticed that some of the fibres are believed to cross from right to left in the optic chiasma, and to pass backward through the opposite optic tract to the brain. When the nerve leaves the commissure it passes out of the cranium through the optic foramen, and reaches the orbital cavity to pierce the sclerotic coat of the lower part of the globe of the eye, and after passing through the choroid coat, opens out and forms a thin nervous expansion termed the retina. The function of the optic nerve is to transmit to the l)raiii the impressions made upon it by external objects, or, in other words, it is the nerve of siglit. Third Pair, Motores Oculorum. — These nerves have their super- fi(-ial origin iu the under surface of the cerebral peduncles. From this point they proceed in a forward direction, and enter the orbit through the foramen lacerum orbitale. This nerve supplies the elevator muscle of the upper eyelid, the internal rectus, the superior and inferior rectus, the retractor oc-uli, and the small oblique muscle. It also gives motor l)ranches to the lenticular ganglion, and through it supplies the ciliary muscle and the circular fibres of the iris. It is cssen- tiallv a motor nerve, and may cause all the parts named to contract. Fourth Pair, Pathetici. — A very thin, long, and slender nerve originating bchinil the corpoia C[uadrigemina, from which it descends in a forward and downward direction to the supra-sphenoidal fissure. By this it is conducted to the pathetic foramen, through which it passes into the orbit, and thence to its ultimate destination, the superior obli(|ue muscle of the e}'e. It is a nerve of motion. Fifth Pair, Trigeminal. — This is much the largest of the cranial nerves, and the variety and importance of its functions imbue it with more than ordinary interest. CKKEBKOSl'INAL XEKVES 393 To commence with, it possesses (l) a sensory and (2) a motor root. The sensory root springs from the anterior part of the pons varolii, and lias upon it a large elongated body, the (rassei-ifm ganglion. From this spring three branches, termed respectively the ophthalmic, superior maxillary, and inferior maxillary nerves. The motor root is the smaller of the two, and is situated on .the inner side of the longer one, with which it takes origin from the pons varolii. From this point it proceeds forward to unite with the inferior maxillary nerve, which is now both sensitive and motor. The superior maxillary division is the largest of the several branches of this nerve; it leaves the cranium through the foramen rotundum. The ophthalmic, which is the smallest, passes out by the foramen lacerum orbitale, and the inferior maxillary division by the anterior opening in the foramen lacerum basis cranii. On emerging from these openings the ophthalmic branch gives off — 1. The Frontal or Supra-Urbital after emerging from the supra-orbital foramen is distributed to the skin of the forehead and the upper eyelid. 2. The Lachrymal Nerve to the lachrymal gland and the muscles and skin of the ear. 3. The Palpebro-Xasal Nerve to the inner angle of the eye, the lachrymal apparatus, and the lower eyelid. It also supplies the membrana nictitans, and sends a branch to the sensitive roots of the ophthalmic ganglion. The Superior Maxillary Nerve emerges from the cranium at the foramen rotundum and enters the superior dental canal. It gives off, among others— 1. The Orbital branch to the eyelids and skin. 2. Great Anterior or Palatine Nerve traverses the palatine canal and is distributed to the hard palate and gums. 3. The Staphyline or Po.sterior Palatine Nerve to the velum palati and soft palate. 4. Na.sal or Spheno-Palatine Nerve to the mucous membrane of the nose. 5. The Dental Nerve to the superior molar, incisor, and canine teeth. 6. The Infra-Orbital Nerve to the nostrils and upper lip, after uniting with a V)rancli of tlit- fr.cial nerve. The Inferior Maxillary Nerve, ;is we have already pointed out, contains both sensory and motor filaments. It gives off — 1. The Masseteric Nerve, to the masseter and temporal muscles. 2. The Buccal Nerve, to the external pterygoid muscle, to the orbital 394 HEALTH AND DISEASE portion of the temporal muscle, the molar glauds, the buccinator muscle, and to the lips. 3. Nerve of Internal Pterygoid Muscle, to the internal pterygoid muscle. 4. tSuperficial Temporal or Subzygomatic Nerve furnishes small fila- ments to the guttural pouch and the parotid gland. It sends a branch to join the seventh nerve as it passes on to the face. 5. The Gustatory Nerve, the larger of the branches of the infei'ior maxillary trunk, is distributed to the mucous membrane of the tongue, and the sublingual and submaxillary glands. This is the nerve of taste. It is joined near its origin by the chorda tympani, a branch of the facial nerve. 6. The Mylo-Hyoidean Nerve to the mylo-hyoideus, and the lower belly of the digastricus. 7. The inferior Dental Nerve enters the dental canal in the inferior maxillary bone, and gives sensory branches to the teeth. 8. The jMental Nerve to the lower lip. Sixth Pair, Motores Occulorum. — This is a small nerve arising from the anterior part of the medulla oblongata, just behind the pons varolii. It proceeds in a forward direction in company with the superior maxillary nerve in order to reach the foramen lacerum orbitale, by which it enters the orbit with the ophthalmic division of the fifth. It gives off a small liranch to the retractor muscle of the eye, and is then distributed solely to the outer straight muscle of the eye (external rectus). Seventh Pair, Portio Dura or Facial. — Arising from the medulla oblongata immediately behind the pons \arolii in company with the eighth. From this point it is directed outward, and, with the eighth nerve, enters at once the internal auditory meatus. Then it passes into the aqueduct of Fallopius, and gives off the chorda tympani nerve to join the lingual, and soon emerges from the stylo-mastoid foramen of the petrous temporal bone. Here it gains the under surface of the parotid gland, from which it reaches the face by passing between the gland and the inferior maxilla ])elo\v its condyle. It blends with the fibres of the sensory subzygomatic branch of the inferior maxillary division of the fifth nerve and forms a plexus (pes anserinus) on the outer side of the masseter muscle. This nerve sujjplies the ear and muscles about the poll, the upper belly of the digastricus, the guttural pouch and jjarotid gland, the stylo -maxillaris, the corrugator supercilii, the orbicularis palpebrarum, the levator labii superioris altvque nasi, and cervical jjanniculus, and CEREBROSPINAL NERVES 395 gives its ultimate fibres to the clieeks, nostrils, and lips. A branch from this nerve joins the infru-orl)ital nerve, and is distril)uted to the upper lip. Eighth, the Auditory Nerve, arises in company with the seventh nerve irom the medulla oblongata, immediately behind the pons varolii. It enters the internal auditory meatus at once, and divides into two branches, one of which is supplied to the cochlea and the other to the vestibule and semicircular canals. This nerve is for the special sense of hearing. Ninth, Glosso-pharyngeal.— This nerve arises from the outer edge of the medulla olilongata, and passes from the cranium through the back part of the foramen lacerum basis cranii. At this point it has upon it Andersch's ganglion, from which the nerve of Jacobson is derived. It now^ descends behind the great cornu of the hyoid bone to reach the base of the tongue, where it supplies filaments to the mucous membrane and sends others to the muscles of the pharynx. Branches given off in its course:- — A very fine filament (Jacobson's nerve), which enters a small foramen in the petrous portion of the temporal lione to be distributed to the tympanum. Two or three filaments to the superior cervical ganglion. A branch which, with some sympathetic filaments, go to the common cai'otid. A pharyngeal branch. This passes to the upper wall of the pharvnx, and, with the pharyngeal filaments of the pneumogastric and sympathetic nerves, forms a somewhat intricate plexus. Tenth, Pneumogastric or Vagus.— This is a most im])ortant nerve, not only on account of its wide distribution, but equally so in reference to the variety and complexity of its functions. It is a mixed nerve, and arises from the side of the medulla oblongata immediately behind the ninth nerve. It then passes out of the cranium through the posterior part of the foramen lacerum basis cranii, where it joins the inner division of the eleventh nerve, with which it unites for about an inch of its course. In the foramen the nerve presents an enlargement — the jugular gan- glion. This gives off the auricular branch of the vagus, which enters the aqueduct of Fallopius to join the seventh nerve, and subsequently pa.sses out with it to be distributed to the lining membrane of the external auditory canal. Below the occipital artery it becomes united with the cervical sympathetic cord, and joined in this way it passes down the neck with the carotid artery as far as the entrance to the chest, where it resumes its independence. From this point it passes onwards above the division 396 HEALTH AND DISEASE of the trachea, and assists in forming tlie bronchial plexus, it now gives off the CBSophageal nerve, which goes to the stomach and the solar plexus. In its course the pneumogastric nerve gives branches — (1) To the superior cervical ganglion of the sympathetic. (2) The pharyngeal branch unites with a branch of the ninth pair given off near the termination of the common carotid, and these, together with a branch of the sympathetic, form the pharyngeal plexus*, which distributes fibres to the pharynx and commencement of the oesophagus. (3) The superior laryngeal nerve enters an opening beneath the appendix of the superior border of the thyroid cartilage, and supplies the mucous membrane of the larynx with sensibility. It also gives branches to the mucous membrane of the root of the tongue, the pharynx, and oesophagus, likewise to the crico-thyroid, and crico-pharyngeus muscles. The inferior laryngeal differs not only in its point of origin, but likewise in the course it subsei.|uently takes. The right inferior laryngeal or recurrent nerve arises from the parent trunk near to the dorso-cervical artery at the entrance to the chest. It passes round the root of this vessel and escapes from the chest between the carotid artery and the trachea, to wliich and the oesophagus it gives filaments. It then passes up the neck in company with the former as high as the larynx, and gives its fibres to the pos- terior crico-arytenoideus, the lateral crico-arytenoideus, the arytenoideus, and the thyro-arytenoideus muscle. Before leaving the chest this nerve gives branches to the cardiac plexus, and communicates with the middle cervical ganglion of the sympathetic. (4) The left inferior laryngeal or recurrent nerve is given off from the pneumogastric opposite the root of the aorta; it then courses its way round that vessel, as did the right round the cervico-dorsal artery. Passing out of the chest between the two first ribs, it follows the carotid artery up the neck to reach the larynx. Here it distributes its branches to the posterior and lateral crico-arytenoideus, the arytenoideus, and the thyro-arytenoideus muscles. It is longer than the right nerve, having to pass round the aorta, and when paralysed gives rise to the disease known as " roaring and whistling". A branch of the pneumogastric amalgamates with the middle or inferior cervical ganglion of the sympathetic, and a pulmonary plexus is formed at the bifurcation of the trachea; branches from it follow the divisions of the bronchi along their ramifications, and others enter into the cardiac i)lexus. Eleventh, Spinal Accessory. — This nerve arises from the whole cervical spinal conl, and passes nj) tlie neck between the .superior and the inferior roots of the cervical spnial ner\es. In its course along the neck CEREBRO-SPINAL NERVES 397 it gradually becomes thicker by the addition of fresh fibres from the cord, and enters the cranium through the foramen magnum. It receives some fibres from the posterior part of the medulla oblongata, and then, united with the pneumogastric for about an inch of its course, passes out through the foramen lacerum basis cranii. Beyond this point the nerve is directed backward beneath the mastoido-humeralis muscle, giving branches to the superior cervical ganglion, the sterno-maxillaris, the mastoido-humeralis, and finally terminates iu the cervical and dorsal trapezius. It is a nerve of motion. Twelfth, Hypoglossal. — Originating from the posterior part of the medulla oblongata the liypoglossal nerve leaves the cranium through the anterior condyloid foramen and descends between the pneumogastric and spinal accessory nerves on the exterior face of the guttural pouch. Passing over the side of the pharynx and larynx it is continued onwards beneath the mylo-hyoid and hyo-glossus brevis muscles, and distributed to all the muscles of the tongue. Soon after leaving the anterior condyloid foramen the hypoglossal nerve receives a considerable twig from the inferior branch of the first cervical pair, and it is further connected with the superior cervical ganglion on the outer part of the guttural pouch. It is a motor nerve, and excites contraction of the muscles of the tongue during feeding or whenever they are required to move. SPINAL NERVES These nerves differ from those last described, in the fact that each of them arises from the side of the spinal cord by two roots — one sensitive, the other motor. The sensitive root is the upper one and has upon it a ganglion. The motor root is the one below. They pass out of the spinal canal together through the intervertebral opening, and then the two roots join their fibres to form a compound nerve, a nerve having motor and sentient properties. Each spinal nerve now divides into a superior and inferior division, and from the latter sends a branch to the sympathetic. Cervical Nerves.— Of these there are eight pairs. The first cervical nerve leaves the spinal canal through the antero-internal foramen of the atlas. The superior branches accompany the occipital artery and vein to between the rectus capitis posticus and the obiiquus capitis superior. At its origin it gives branches to the small muscles about the poll. The inferior branch passes downwards and is distributed to the thyro-hyoid, subscapulo-hyoid, sterno-thyroid, and sterno-hyoid muscles. It sends a small branch to the hypoglossal nerve, and another to the superior cer- 398 HEALTH AND DISEASP] vical ganglion of tlie sympathetic. It also supplies the skin of the ear on the inner and lower part. The second cervical nerve leaves the spinal canal through an opening at the anterior part of the dentata, under cover of the ohliquus capitis inferior. The inferior branches of this nerve are distributed to the mastoido-humeralis and skin of the ears; the superior branches go to the superior and inferior oblique muscles of the neck. The sixth and seventh, and sometimes the fifth, together with a branch from the brachial ple.Kus, form the diaphragmatic nerve. From the second to the si.xth they communicate with each other, and then divide into three sets of branches; one set joins the vertebral nerve, and goes to the sympathetic or middle cervical ganglion, another is distri- buted to the mastoido-humeralis, longus colli, rectus capitis anticus major, the scalenus, and to the phrenic nerve, and a third to the skin. The sixth nerve also furnishes branches to the levator anguli scapulae and rhom- boideus muscles, and the brachial plexus receives a twig from its phrenic branch. The superior branches of the last six cervical nerves supply the splenius, trachelo-mastoideus, semi-spinalis colli, and complexus muscles, and the skin in the region of the mane. The seventh and eighth cervical nerves are expended in the formation of the brachial plexus. Each nerve supplies a branch to the middle cer- vical ganglion, the former joins the vertebral nerve, the latter pas.ses directly to the ganglion. BRACHIAL PLEXUS The mixing or joining together of nerves to form plexuses is one of the methods which nature adopts in order to establish a material relation of distant parts, and to some extent a dependency of one part upon another, so that the whole shall be capable of co-ordinating and acting simul- taneously and together. The brachial plexus is a large fasciculus or bundle of nerves resulting from the combination of the inferior divisions of the last three cervical and first two dorsal roots. It is chieHy intended for the supply of the fore-limb with the nerves which animate it. The branches going to make up the brachial plexus converge together after leaving the spine, the dorsal division winding round the front of the first rib and joining the cervical portion to form a bioad flat band which passes between the superior and inferior heads of the scalenus muscle, and subsequently breaks up into the following branches: — 1. The Diaphragmatic. 2. The Suprascapular Nerve. 3. Nerves to the Pectoral Muscles. MEKVEs, Ai;ri:i;ii:s, I. Inner 1. Os iiinoniinatuin. 2. Gracilis. 3. Rectus femoris. 4. Vastus iuternus. 5. Sartorius. 6. Popliteus. 7. Flexor nietatai'si. 8. Extensor pedis. 9. Flexor pedis perforans. 10. Flexor jjedis accessorius. 11. Gracilis. 12. Semitendiuosus. 13. Semimembranosus. .V.\l» MUSCLES OF THK LLMBS— II Asi'ECT OK Thigh and Leg 14. Adductor parvus. 15. Pectineus. 16. Adductor magnus. A. Branch of obturator uerve. B. Brauch of deep femoral artery. c. Femoral artery. 1). Bifurcation of posterior tibial neive into internal and external plantar nerve. E. Anterior crural nerve. F. Branch of femoral artery to (juadriceps. G. Beep femoral artery. II. Prepubic artery. II. Outer x\^pe(T of Hind-Lijib 1. Anterior tibial artery. 2. Large metatarsal artery. 3. Internal metatarsal vein. 4. Coronary plexus. 5. Digital vein. 6. Digital artery. 7. Perpendicular artery. 8. Large metatarsal bone. !). Small metatarsal bone. A. Flexor metatarsi. B. Extensor pedis, c. Extensor brevis. D. Lumbricalis. E. Flexor pedis perforans. F. Flexor pedis [lerforatus. 0. Gastrocnemius. H. Flexor pedis. 1. Peroneus. NERVES, ARTERIES, AND iMUSCLES OF THE LIMBS-II I. Inner Aspect of Thigh and Leg. H. Outer Aspect of Hind Limb. CKKKliKOSl'lNAL NERVES 399 4. Nerve to the Subsciipularis. 5. Nerves to Serratus Magnus and Levator Scapulis. G. The Circiimrtex Nerve. 7. Nerves to Teres Major and Latissimus Dorsi. 8. The Musciilospiral Nerve. 9. The Median Nerve (two roots). 10. The Ulnar Nerve. 11. The Snhcntaneon.s Thoracic Nerve. The Phrenic or Diaphragmatic Nerve is formed mainly by the union of the aixtli and .seventh cervical nerves, and sometimes also by a small branch of the fifth. It then enters the chest by passing between the two first ribs, and crossing the pericardium reaches the diaphragm, where it terminates. It is a motor ner\"e to the diaphragm. The Suprascapular Nerve is short and somewhat thick. It is derived from the sixth, seventh, and eighth cervical roots, and pa,sses between the supraspinatus muscle and the subscaj)ularis. After winding round the anterior border of the scapula it gives branches to the supra- spinatus, and is nltimatelv expended in the infra-spinatus. The Anterior Deep Pectoral Muscle receives its nerve supply from the seventh and eight cervical nerves, while the superficial pectoral muscle obtains its fibres from the two roots of the median. A branch also pas,ses to the posterior deep pectoral, and another longer and thicker follows the course of the spur vein. Nerve to the Subscapularis. — All the cervical roots of the brachial plexus contribute to form the nerve going to the subscajiularis. After crossing the supra-spinatus some of the fibres pass between it and the subscapularis, and the rest are distributed to that muscle. Nerve to Serratus Magnus is derived from the seventh and eighth cervical nerves, M'hich pass through the upper division of the scalenus muscle, and uniting distribute branches to the serratus maguus muscle. Nerve of the Teres Major is a small nerve situated beneath the shoulder on the inner face of the subscapularis. It springs from the seventh and eighth pairs in common with the circumflex nerve, and gives its fibres to the teres major. Latissimus Dorsi branch. — A long nerve situated beneath the .scapula, and derived mainly from the root of the eighth cervical nerve, and to some extent also from the dorsal roots of the brachial plexus. It crosses the subscapularis and teres major to gain the lati.ssimus dorsi, where its fibres are expended. Nerves to the Levator Anguli Scapulae. — The levator anguli scapula?, together with the rhoml)oideus, receive their supply from the 400 HEALTH AND DISEASE inferior branch of the sixth cervical nerve, and the levator also receives a slight contribution from the seventh. Radial or MuSCUlo-Spiral Nerve. — This nerve derives its fibres from the seventh and eighth cervical pairs, and also from the first dorsal root. It is the largest of the branches furnished by the brachial plexus. From its point of origin it passes downwards, crossing over the inferior part of the subscapularis and the teres major muscles. It then dips down and takes an outward course under the great head of the triceps, winding round the humerus in the musculo-spiral groove to gain the front of the elbow-joint, where it is found beneath the extensor metacarpi and extensor pedis muscles. In its course it gives branches to the great and small heads of the triceps, and to the scapulo-ulnaris muscles, the caput medium, and anconeus. Its terminal branches are destined to the extensor metacarpi magnus, riexor metacarpi externus, the flexor pedis, extensor os suffraginis, and skin. Median Nerve. — The median nerve is formed by the union of two branches: one comes from the sixth, seventh, and eighth cervical, the other from the eighth cervical and the first dorsal. It passes down the limb at first in front of the humeral artery, and continues its downward course in company with the posterior radial artery until a short distance abo^■e the knee. Here it divides, the inner branch forming the internal plantar nerve, the outer uniting with the ulnar to form the external jjlantar nerve. Its branches are distributed to — 1, the superficial pectoral; 2, a consider- able branch which passes between the coraco-humeralis, to which it gives fibres, and expends itself in the biceps; 3, a branch which leaves the parent trunk at the middle of the humerus, goes to the brachialis anticus, and sends off a branch to the skin of the forearm; 4, to the flexor metacarpi internus and the flexor pedis perforans and perforatus. The Ulnar Nerve. — This nerve is chiefly derived from the dorsal roots of the brachial plexus. It is less considerable in size than the one just described. Placed behind the humeral artery, it dips down beneath the scapulo-ulnaris, between it and the caput parvum, to reach the posterior part of the inner condyle of the humerus. From this point it proceeds to the back of the forearm, and following the posterior border of the ulnaris accessorius, terminates by joining a branch of the median just above the knee. It assists in forming the external plantar nerve, and gives some twigs to the front of the carpus. The branches given off" in its downward course supply the superficial jjectoral nniscle, the skin of the forearm, and, excepting the external and internal flexors of the meta- carpus, all the muscles behind the radius. Subcutaneous Thoracic Nerve. — A long slender nerve situated CEKEBRO-SPINAL NERVES 401 on the side of the chest bencatli the pannicuhis and above the spur vein, whose course it follows, to be lost in the pannieulus of the tlank. It is formed mainly of the dorsal roots of the thoracic plexus, and to a small extent from the eighth cervical nerve. In its course backwards it gives ofl' branches which anastomose with the second and third perforating intercostal nerves, and forms a net-work over the inner surface of the pannieulus. The pannieulus extending over the shoulder and arm receives fibres from this nerve. Circumflex or Axillary Nerve. — This is a nerve of considerable size; it is derived from the seventh and eighth cervical roots, and after crossing the subscapularis soon enters the interspace between that muscle and teres major. It then passes behind the shoulder joint, accompanied by the posterior circumfiex artery, and disti'ibutes its branches to the teres minor deltoid, mastoido-humeralis, and ultimately reaches the integument in front of the ■ arm. Behind the shoulder it gives small twigs to the scapulo-humeralis posticus. Dorsal Nerves, eighteen pairs. — These nerves on issuing from the spinal canal divide into two sets of branches, as we saw occur in the case of the cervical nerves. The upper divisions, which are the smaller, ascend to reach the dorsal muscles and skin of the back, to both of which they are distributed. The inferior divisions descend, and having gained the intercostal spaces, pass downwards along the posterior border of the ribs beneath the pleura as the intercostal nerves. In their course they give branches to the pannieulus and skin, and the first seven or eight terminate in the pectoral muscles and skin cover- ing them, and the last ten are distributed to the rectus abdominis, the transversalis abdominis, and the skin of the belly. The first and second intercostal nerves send branches to the brachial plexus from their inferior divisions. Lumbar Nerves, six pairs.— The lumbar nerves, like the dorsal, divide, after leaving the spinal cord, into a superior and inferior branch. The former, passing in an upward direction, ramify through to the muscles of the loins, and ultimately reach the skin, where they terminate. The inferior branches are variously distributed. Those of the first two, after supplying the psoas magnus, pass over the edge of that muscle, and are distributed to the muscles of the flank, the skin, and some fine filaments to the muscles of the thigh. The inferior branch of the third nerve supplies the psoas magnus, psoas parvus, and quadratus lumborum, and its ultimate fibres are expended in the skin of the thigh. The fourth, fifth, and sixth lumbar branches contribute to form the lumbo -sacral 402 HEALTH AND DISEASE plexus. All the inferior branches of these nerves are connected with the great sympathetic. Sacral Nerves, five pairs. — There are five sacral nerves. The first four pass out of the spinal canal by the sacral foramina, and the fifth by the opening between the last sacral foramen and the first coccygeal bone. After emerging from the spine, they each divide into a superior and an inferior branch. The former of these pass upwards through the supra-sacral openings, and are distributed to the muscles on the side of the sacral spine and to the skin of the croup. The lower branches are much the larger of the two, and pass in a direction downwards and back- wards, to be distributed as follows: — The first and second, by joining with the third, fourth and fifth lumbar, form the lumbo-sacral plexus. The third and fourth pass along the inner side, or even within the texture of the sacro-sciatic ligament, and are joined together by a branch going from one to the other. The third forms the internal pudic nerve, which winds round the ischial arch, and with its fellow on the opposite side gains the dorsal border of the penis, along which it runs, and ends in the mucous mem- brane covering the glans penis. In its course from behind forward it gives numerous branches to the corpora cavernosa and the urethral canal, and while in the pelvis, two small ramuscules go to the perineal region, and hfemorrhoidal branches to the anus. The fourth, together with a branch of the third, innervates the sphincter muscle of the anus and surrounding skin, and the fifth, after giving a branch to the first coccygeal nerve, is expended in the muscles and in- tegument about the base of the tail and the root of the penis. Coccygeal Nerves. — These number five or six pairs, which decrease in volume from the first to the last. The first coccygeal communicates with the last sacral nerve, and then with others passes backwards, and is expended in the muscles and skin of the tail. LUMBO-SACRAL PLEXUS This is a combination of nerves for the supply of the hind-limb. It corresponds with the brachial plexus of the fore-limb in being formed by the inferior branches of the fourth, fifth, and sixth lumbar, and the first and second sacral nerves. The branches given off from this plexus are as follow: — 1. IliaCO-MusCUlar Branches. — Small branches given to the psoas magnus, psoas parvus, and iliacus muscles. 2. Anterior or Great Crural Nerve. — This is a nerve of considerable ANATOMY OK llORSK'S HEAD Fig. I Seventh nerve. Posterior auricuhir vein. Anterior auricular vein. Temporalis muscle. Corrugator supercilii. Orbicularis palpebrarum. Levator labii superioris al.i'que nasi. Levator labii superioris propiiu.s. Dilatator iiaris lateralis. Orbicularis oris. Zygomaticus. Depressor labii inferioris. Buccinator. Stenson's duct. Submaxillary artery. Submaxillary vein. Maaseter muscle. Temporal vein. Maxillo-muscular artery. Parotid gland. Submaxillary vein. Jugular vein. . Maxillo-muscular vein. Fig. TT A. Common carcjtid artery. B. External carotid artery, c. Internal carotid arteiy. D. Occipital artery. E. Internal maxillary artery. F. Superficial temporal artery. 0. Posterior auricular artery. II, n. Right and left submaxillary artery. HI'. Hyoid bones (divided). 1, I. Right and left submaxillary veins. J. Buccal vein. K. Alveolar vein. L. Buccal plexus. M. Infra-orbital nerve. N. Superior maxillary nerve. o. Inferior maxillary nerve. p. Inferior dental nerve. Q. Lingual or gustatory nerve. R. Mylo-hyoid nerve. s. Masseter nerve. T. Ophthalmic nerves and vessels. u, u. Glosso-pharyngeal nerve. V. Submaxillary gland. vf. Thyroid gland. X. Section of lower jaw. r. Tempero-maxillary articulation. z. Hypoglossal or twelfth nerve a. Lajynx. ANATOMY OF THE HORSE'S HEAD CEREBEO-SPINAL NERVES 403 size formed by fibres from tlie fourtli and tiftli lumbar roots, and in part also from the loop between the third and fourth. Descending between the psoas raagnus and parvus, it passes downwards at the outer side of the external iliac artery under cover of the sartorius, and after crossing the conjoined tendon of the psoas and iliacus muscles, ends in a number of branches, which pass between the vastus internus and rectus femoris to be distributed to the extensors of the legs. It gives oft' the internal saphenous nerve, and sends branches to the rectus femoris. 3. The Obturator Nerve is situated beneath the peritoneum on the inner side of the pelvis, and follows the course of the artery of the same name through the obturator foramen to the internal aspect of the thigh. It is derived from the fourth and fifth lumbar roots, and gives branches to the obturator externus, adductors of the thigh, the pectineus and gracilis muscles. 4. The Anterior and Posterior Gluteal Nerves, also called the small sciatic nerves. These nerves leave the pelvis by the great sciatic notch. The anterior gluteal consists of four or five branches, which are distributed to the gluteus medius, the tensor vagina femoris, vastus ex- ternus and internus, and the gluteus externus. The posterior gluteal nerve is represented by two branches — a superior and inferior. The superior supplies the superficial gluteus, the middle gluteus, and the biceps femoris. The inferior branch, after passing over the outer side of the tuber ischii, is destined to the skin of the thigh, the semitendinosus, and with a branch of the internal pudic nerve to the structures of the perineum. The Great Sciatic Nerve is the largest in the body. It is derived from the lumbo-sacral plexus, and issues from the great sciatic opening as a broad white band ; thence it takes a downward course between the sacro-sciatic ligament and the gluteus maximus. On reaching the thigh it is lodged between the biceps femoris and semitendinosus, having the semimembranosus and great adductor of the thigh supporting it within. On nearing the leg it passes between the two heads of the gastrocnemius muscle, when it takes the name of the internal popliteal nerve. This is continued on as the posterior tibial, which dividing, forms the internal and external plantar nerves. In its course down the limb it supplies a slender branch to the obturator internus, pyriformis, gemelli, and quadratus femoris. The External Popliteal Nerve is a branch of considerable size given off from the great sciatic near to the gemini muscles. It then passes downward and forward between the biceps femoris and the outer head of the gastrocnemius. On reaching the outer lateral ligament of the stifle it divides into the musculo-cutaneous nerve and the anterior tibial. i04 HEALTH AND DISEASE The Musculo - Cutaneous branch is situated beneath the tibial aponeurosis. It passes down the leg along the union of the peioneus and extensor pedis, and ultimately is distributed to the skin on the outer side of the metatarsus. In its course it gives branches to the peroneus. The Anterior Tibial Nerve, after leaving the one last described, passes underneath the extensor pedis muscle, and having supplied branches to it, the flexor metatarsi, and short extensor of the foot, continues its course downwards in front of the leg as far as the hock joint; it then accompanies the large metatarsal artery, and finally ends in the skin on the outer side of the canon. The Internal Saphenous Nerve. — This is a branch of the anterior crural nerve, from which it is given off at the brim of the pelvis. From this point it passes downwards in company with the femoral artery, and gives branches to the sartorius muscle. About the middle of the thigh it reaches the surface by passing between the last-named muscle and the gracilis, accompanied by the saphenous vein and artery. It divides into an anterior small and a posterior larger branch, which supply the inner and front and the posterior and back parts of the thigh respectively. Its ultimate fibres are distributed to the skin on the inner and back part of the leg as low as the hock. The External Saphenous Nerve leaves the great sciatic, and passes over the outer head of the gastrocnemius under cover of the biceps femoris, where it receives a branch of the external popliteal nerve. It then passes down the leg in company with the saphenous vein on the outer and front part of the gastrocnemius tendon, and continuing its course over the hock joint, is ultimately expended in the skin of the outer part of the metatarsus. The Internal Popliteal Nerve. — This nerve consists of a bundle of nerve branches proceeding from the great sciatic. Passing downwards and forwards between the two heads of the gastrocnemius muscle, it gives branches to it, to the flexor perforatus, the soleus, the perforans, and flexor pedis accessories. Finally it gives off a long branch, which passes between the perforatus and the inner head of the gastrocnemius as the posterior tibial nerve. The Posterior Tibial Nerve. — The posterior tiljial is a branch of the intei'nal popliteal. In passing down the leg it is situated beneath the inner head of the gastrocnemius. It then becomes enclosed in the deep fascia of the leg, on the inner side of which it descends, and at the hock divides into two parts to become the internal and external plantar nerves. These enter the tarsal sheath in company with the plantar arteries, and separate from each other behind the hock. DISKASES UK THE NERVOUS SYSTEM 405 From tliis point they proceed down the leg along with the perforans tendon, and divide as in the fore-limb to supply the foot. The Anterior Tibial Nerve commenees on the outer side of the stifle joint, and dips down between the peroneus and extensor pedis muscle, under cover of which it passes down the leg. On reaching the hock it bears outwards, and, together with the large metatarsal artery, passes down the limb to the fetlock joint, and expends itself in the skin on the outer side of the os sufiraginis. It gives branches to the extensor pedis and flexor metatarsi, and on reaching the front of the hock some twigs to the extensor brevis. DISEASES_ OF THE NEEVOUS SYSTEM Affections of the central nervous system, including the brain and spinal cord, must necessarily be of a very grave character. Physiologists allow that the brain is chiefly -concerned with the mental functions, but, in addition, it also presides over special movements, some of which are volun- tary while others are of the excito-motor character. Derangement affecting any important part or nerve centre, either in the form of excess or de- ficiency of blood, undue pressure, or structural changes, produces either exalted function, or drowsiness going on to stupor, or paralysis. Disease of the cerebellum or smaller brain causes giddiness and failure of the normal power to regulate the functions of locomotion. The causes of cerebral derangement are numei'ous. As the brain pre- sides over many important functions of the body, it is also sympathetically affected when the organs which perform those functions become the seat of structural or functional changes due to accident or disease. The brain is invested by certain membranes which afford protection on the one hand, and on the other act as a medium through which pass the vessels carrying the necessary supply of blood for the nourishment of its tissues and the exercise of its function. CEREBRITIS AND MENINGITIS Very early in the history of veterinary science the French writers separated diseases of the brain into two distinct forms, which were desig- nated by different terms — cerebritis when the substance of the brain was affected, and meningitis when the inflammation attacked the membranes (meninges) which cover the brain. The necessity for the distinction was at one time disputed, but it is now quite clearlv recognized; in fact, the two conditions of disease are 406 HEALTH AND DISEASE indicated by totally different symptom.s. When inflammation afl'ects the intimate structure of the brain the prominent signs are loss of sensibility and consciousness more or less complete, and various degrees of paralysis. None of these symptoms are present in inflammation of the meninges, of which violent excitement, pain, tenderness, delirium, and convulsions are the chief manifestations. In the case of disease being (-onfined to the brain there is seldom any marked disturbance in the circulatory system, but in meningitis both the pulse and respiration are excited in a high degree. To put the dirt"erences concisely, it may be said that in disease of Fig. 177. — Sleepy Staggers the brain substance, diminished sensibility, loss of power of motion, and deranged volition are the characteristic features, while inflammation of the investing membranes of the organ is indicated by spasms, convulsions, violent pain, delirium, and frenzy. Impaired consciousness may arise from disease of the stomach. The affection which is described as " stomach staggers " might probably be, in popular phrase, referred to as a sick head- ache due to an attack of indigestion, the brain being sympathetically affected. The symptoms of the disorder are generally observed after a full meal, which the horse probably swallows rapidly owing to a previous long fast. The first indication is a slight dulness, the eyelids being drooped, and the nose rested against the manger. If compelled to move, the animal staggers- hence the name given to the disease. In very pronounced cases the drowsiness may be followed by delirium, or sometimes severe convulsive twitchings of the muscles. Now and then a violent excitement supervenes, and the animal throws himself about DISEASES OF THE NERVOUS SYSTEM 407 in vivrious directions in a condition of ;ictiud ficnz}-. In some of these erratic movements the horse may injure himself, or the attendant if he happens to come in his way, but it is evident that tliere is no intention to do mischief. The treatment of the disease, to be successful, must be adopted as soon as the first indications are apparent. The animal should be removed to a loose-box and freed from all restraint; food should be kept out of his reach, but he may be allowed to drink any quantity of water. In former times the treatment on which the greatest reliance was placed was the immediate employment of the lancet and the withdrawal of a large quantity of blood. This system, however, has been discontinued for many years past, and instead it is usual to rely on the administration of a strong aperient, together with antiseptic agents, as hyposulphite of soda. Four to six ounces of solution of aloes, or more, according to the size of the horse, forms a useful purgative; and if the drowsy condition is extremely marked, aromatic spirit of ammonia in doses of from one to two ounces every two or three hours, while the condition remains, is likely to be effective. Benefit will also be derived from sponging or douching the head with cold water at short intervals, or by the application of ice-bags to the poll. VERTIGO Vertigo, megrims, or giddiness may be associated with organic disease of the brain, or be occasioned by derangement of the liver or other organs of the digestive system. A fit of vertigo may also arise from the action of the sun's rays upon the unprotected head, or it may be due to the retention of blood in the vessels of the brain consequent upon pressure of a tight collar. A single attack, which may occur at any time during a journey, is sometimes difficult of explanation; when a hot sun and a tight collar are both present they will naturally be looked upon as the cause of the fit, but in the absence of either it will be impossible for anyone to decide whether it was due to some chronic disorder in the brain or to derangement of the digestive organs. In these cases a direct diagnosis is only possible when the history of the animal is knowm. It may, however, be suggested that a sudden and violent atta(;k, under the influence of w^hieh the horse suddenly stops, raises and shakes his head, and then drops down in a state of partial unconsciousness, is most likely to be consequent on some cause which is acting at the moment, such as heat,' pressure on the vessels of the neck, or some acute disturbance of the liver. Vertigo which arises from organic disease of the nervous centres, is in most cases a disorder of gradual development. The first attack is extremely 408 HEALTH AND DISEASE slight, and probably attracts very little attention; the driver may notice that the horse occasionally shakes his head, or turns it to one side as though he were annoyed by something which had entered the ear; after a short time the animal ceases to behave strangely, and finishes the journey with- out any further indication of disturbance. Nothing more may be thought of the matter until the recurrence of the attack after the lapse of a week or Fig. 178. — Vertigo or Megrims more, and even then no suspicion of megrims is probably excited until a more severe attack occurs. Post-mortem examinations have been made of horses which have suffered from chronic vertigo, the fits occurring at intervals of a few weeks or months during several years of the animals' lives. The results of such examinations were in some cases unsatisfactory; in others calcareous nodules and tumours, varying in size from a pin's head to a pigeon's egg or larger, have been found in the plexus of vessels in the lateral ventricles of the brain. Frequently, however, the search for morbid appearances in the brain and spinal cord has been attended A\ith disappointment. Attacks of vertigo may sometimes happen in consequence of injury to the head; a blow accidentally or intentionally inflicted may produce DISEASES OF THE NERVOUS SYSTEM 409 slight concussion, or may even result in the depression of some of tlic bones forming the cranial cavity, in which case stupor will result, and will con- tinue until the depressed portions of bone are elevated by means of a surgical instrument. When the injury is slight, the fit of giddiness which follows generally passes off in a short time and leaves no trace behind; but the rider or driver, being prol)ably unaware that the animal has been struck on the head, is disposed to look upon the attack as a case of megrims of the ordinary kind. The fact, however, of the attack not recurring would be a sutiicieiit evidence that the injury is not permanent. Treatment. — As the occurrence at irregular intervals of fits of vertigo is at the least annoying, and cannot be said to be unattended with danger to tiie rider or driver, it is naturally a subject of enquiry as to what can be done in the way of prevention. If any positive cause, such as a tight collar, is detected, the remedy is of course perfectly obvious. Should symptoms of disease of the liver be present, a dose or two of aloes with calomel may be given with benefit; but if there is no obvious cause, the conclusion will necessarily be that there is some morbid condition of the central nervous system, and beyond attending to the animal's general health by judicious feeding and properly regulated work or exercise, nothing can be done. Horses suffering from chronic brain disease should never be hurried or called upon to undergo severe exertion. Moreover, they should be fed two or three hours before being employed in any kind of work, and food should be given in small quantities and often. ABSCESS IN THE BRAIN A more serious result of a blow on the head is the formation of abscess in one of the hemispheres of the brain, or inflammation of the membranes, which is usually indicated by violent excitement. Abscess in the brain also occurs not uncommonly when, in consequence of a vessel being punctured in the act of opening an abscess, a quantity of pus may get into the blood- stream, causing the condition which is known as pycBmia. Abscesses in various parts of the body are the result of this contamination of the blood, and the brain is a very favourite situation for the deposit of jaus. The first indication of the occurrence is the appearance of drowsiness, gradually increasmg to unconsciousness, in which condition the animal dies. No treatment is likely to be of any avail. 410 HEALTH AND DISEASE EPILEPSY Epilepsy, eclampsia, catalepsy, and chorea (St. Vitus' dance) are all disorders of the nerve centres, and are associated with eccentric muscular action, and often with derangement of eonsciousnoss, but horses are very rarely attacked by any of them. Epilepsy is a peculiar affection almost unknown in the horse, but not uncommon in the dog. The exact pathological conditions of the brain or spinal cord on which the intermittent attacks or epileptic fits depend are not known. It is even uncertain whether the origin of the malady is centred in the brain or spinal cord, although recent experiments lend considerable force to the view of the brain rather than the spinal cord being the seat of the derangement. Characteristic epileptic fits may be produced in dogs while under chloroform after complete disconnection of the brain from the spinal cord. Injection of a minute dose of absinthe into the circulation in an animal thus prepared is quickly followed by all the .signs of epilepsy, and dogs utter maniacal cries, which, of course, are purely the result of reflex action, the dog being at the time unconscious. The Symptoms of an epileptic fit are well known. Usually there is no marked premonitory sign of an approaching attack. An animal in a state of health, apparently, may suddenly reel and fall over on its side, in the case of a dog uttering cries which soon cease, while the whole muscular system is in a state of convulsive action. Urine and faeces are involun- tarily discharged; a quantity of foam collects about the mouth. In a short time the convulsions cease and the animal regains consciousness, and is soon restored to its ordinary condition, showing no further symp- toms of illness until the sudden occurrence of another fit. Considering the great difticulty of disconnecting severe forms of megrims in the horse from epilepsy, it is not remarkable that some writers record cases of equine epilepsy. It is, however, rarely if ever the case that the horse suffers from this disease, and certainly not in that typical form in which it is seen in the dog. Several forms of epilepsy are described by writers, for example, spon- taneous, symptomatic, traumatic, and refiex epilepsy, and in all these the attack may be serious or benign. Spontaneous epilepsy is the result of functional disturbance of the brain, amounting to general irritability, which disposes the subject to an attack under trifling influences, such as fear or any kind of mental excitement. Horses are said to have suffered when alarmed by a display of fireworks, or the passing of a train, or from suddenly passing from a subdued to an intense light. Symptomatic epi- lepsy is the form of the disease which is associated with structural changes DISEASES OF THE NERVOUS SYSTEA. +11 ill the ceiitnil noivous system, as thickening of the membranes ol tlie biaiii, deposits of pus, or the presence of parasites. Traumatic epilepsy is due to injury, as, for example, blows upon the cranium causing compression of the nerve structures from effusion of blood or the depression of the bony boundaries of the cavities in which the brain and spinal cord aic contained. ReHex epilepsy may occur in consequence of irritation affecting the terminal branches of nerves in remote parts. Such irritation depend- ing upon pressure exercised by foreign bodies, irritation caused by parasites in the digestive organs, affections of the mouth due to the changes which occur in course of dentition. All the above forms of epilepsy, when con- nected with special liability to nervous excitement, may be considered as hereditary. ECLAMPSIA This disease borders so closely upon the one previously considered, epilepsy, that its manifestations are allowed to be identical with those of reflex epilepsy. It is also stated that eclampsia may be transferred into true epilepsy; the main distinction appears to be that the convulsive spasms affect chieffy the extensor muscles, and appear without any disturb- ance of the mental conditions and independent of any structural alterations. In fact, the disease is really one of pure motor-nervous excitability. CHOREA (ST. VITUS' DANCE) This disease is perfectly well known as it affects the dog. It is fre- quently one of the results of distemper; its chief manifestation is constant rhythmical contraction and spa.sm of some of the muscles of the neck or extremities, usually the fore extremities. Animals which suffer from this disease frequently retain their health for a considerable time, but when chorea affects dogs which have recently recovered from distemper, the constant excitement arising from the incessant muscular spasms interferes with the complete restoration of the animal, and occasionally ends in fatal paralysis. Cases of localized muscular spasm have been described in the horse under the name of chorea, but it must be allowed that the disease in that animal, if it occurs at all, is extremely rare. STRINGHALT This condition, which is vcrv well known to horsemen, is another of the ill-defined affections of the nervous system. The condition is indicated by spasmodic movement of the muscles of one, sometimes of both liind-legs, and occasionally one or both of the fore-legs. The efi'ect of tlie sjmsm is to 412 HEALTH AND DISEASE cause an extraordinary jerking upwards of the affected extremities, after which the foot is brought forcibly to the ground. The disease differs from chorea, as the symptoms are only developed during pro- gression, whereas in chorea the muscular spasms are constant even during sleep. In some cases stringhalt is only exhibited occasionally and under special conditions, as when the horse is made to turn sharply round, or when observed while quietly moving in his box, but it generally becomes more pronounced as the animal advances in age or when he is excited. No treatment has been found to be effective in controlling the muscular movements. APOPLEXY In very hot seasons horses which are called upon to undergo violent exertion are likely to suffer from cerebral derangement due to determina- tion of blood to the vessels of the brain. This condition is correctly descril)ed as sunstroke. According to the duration of the active causes the final consequences will vary. In the first instance, symptoms will consist of dulness, general depression varied by periods of excitement. If the causes continue, the voluntary movements of the animal may be interfered with, and finally it may fall in a state of unconsciousness. The worst consequence which is to be apprehended is the rupture of some of the overcharged vessels of the brain and escape of blood into the tissue of the organ. If the hemorrhage is sudden and considerable the result will be an apoplectic fit, which may be immediately fatal. The fit will probably be preceded by an irregularity in the animal's movements, trembling, turning round or backing, ending in a sudden fall, loss of consciousness, and possibly death in a few minutes. A partial recovery may, however, take place, and the animal may live for some days or weeks, but a fatal result is almost certain to follow. When the hemorrhage is slight the symptoms will be those which have previously been described, i.e. irregular movements followed by drowsiness, from which the animal will gradually recover, but in such instances a small clot of blood may be left in the substance of the brain and lay the founda- tion for future mischief Treatment. — On this subject a great difference of opinion exists; bleeding and cold applications are advocated, or, on the other hand, stimulants are suggested in order to overcome the drowsy and depressed state into which the animal has fallen. It is probably the case that ice- bags to the head and bleeding would be beneficial when the animal is DISEASES OF THE. NERVOUS SYSTEM 413 suri'c'iing from an apoplectic fit, wliile the use of stimulants miglit be resorted to when the more urgent symptoms have ceased. In all cases where the power to swallow exists, a strong dose of physic should be promptly administered. CRIB-BITING In connection with diseases of the nervous system it is necessary to refer to certain abnormal actions commonly described as nervous habits, which are not usually recognized as diseases, but which, as they are not normal, i.e. are not in accordance with the rule as applied to the actions of healthy animals, must be classified as abnormal. " Cribbing " or " tic ", " wind-sucking ", and " weaving " may be taken as examples of diseases which are more or less connected with some ill-defined derangement of the ner- ^ vous system. Tic or cribbing has -sJ^^m been carefully studied in its various - ^^ forms by Continental veterinarians. -'' k^, Friedrich Berger and Frohne, in s\ their work on the pathology of the domestic animals, allude to the causes of cribbing as being complex and variable in their nature. Idle- ness is said to be one cause of the acquirement of the habit. Horses, Fii; iro.-xhroat-strap for cribbiting like other creatures, are supposed to invent some kind of pastime when left alone in a stall or box, and the manger, drinking-trough, or piece of chain or rope lends itself to this kind of indulgence. In the case of some animals it seems that no assistance from external objects is necessary, as they succeed in per- forming the actions of a crib-biter without seizing the manger with their teeth or obtaining any other support. By contracting the muscles of the neck they contrive to keep the head in a fixed position, and can make the peculiar noise which is common to crib-biters. Among the causes of cribbing heredity is referred to as having con- siderable influence. Horses it is said become crib-biters and wind-suckers apparently from imitation, although it would seem that a certain amount of nervous excitability is necessary as a predisposing cau.se, as it may be that only one animal out of a very large number which are exposed to the same temptation acquires the habit. The halnt of cribbing or wind-sucking has somewhat fancifully been 414 HEALTH AND DISEASE attributed to the use of a curry-comb in the act of cleauing, as when the instrument is used with much force it causes a good deal of irritation, which the animal indicates by biting at anything within its reach; and it is supposed that the habit of biting and making spasmodic movements of the lips and other parts at the same time might finally lead to cribbing. Cribbing and so-called wind-sucking induce occasional attacks of colic from the quantity of air which is developed in the stomach, and both are associated with an irritable condition of the mucous membrane of the digestive organs, which we believe to be a cause of these remarkable acts. In a legal point of view cribbing and wind-sucking would amount to unsoundness if that term is construed strictly, and in some parts of the Continent the habit is recognized as sufficient to constitute a breach of warranty. In any case, a horse addicted to crib-biting or wind-sucking, or both, can hardly be said to be as useful for its intended purpose as an animal which is free from such defects. If there were no other objection to be urged, it would be sufficient to point to the well-known fact that the animal loses flesh and becomes thin. Treatment. — The owner of a crib-biter or wind-sucker is very anxious to find out some means of cure, and various mechanical appliances have been suggested for the purpose. The plan of using movable mangers and troughs, and avoiding all projecting posts on which the animal may place his teeth and get a point of support, has been said to be successful in cases of crib-biting, but it is obviously of no use in the case of a wind- sucker, which does not require such assistance. In most instances of crib- biting and wind-sucking the ordinary throat-strap (fig. 179), which is arranged to be buckled round the throat, acts as a preventive, but to be effectual it must be constantly employed while the animal is in the stable. The other habit which has been referred to under the term iveaving, consists in swaying the head and fore part of the body from side to side like a bear. Although perhaps less objectionable than wind-sucking, it is, nevertheless, a serious fault, since the animal which is addicted to it is constantly using his legs when he should be resting them. Weaving is most commonly seen in horses which are tied to the manger by means of two side-ropes fixed to the head-collar and carried through rings on each end of the manger. At the end of each rope a perforated wooden block is fixed on purpose to prevent the removal of the halter -ropes from the rings. The habit of weaving mav sometimes be corrected l)v keeping the animal in a loose-box without any head-collar or halter-ropes. This, how- OEDEMA OF CHOROID PLEXUS BRAIN TUMOUR DISEASES OF THE NERVOUS SYSTEM 415 ever, is not always successful, as in some cases the animal continues the lateral movements of the head even when it is left altogether without any means of restraint. TUMOURS IN THE BRAIN AND CRANIUM Tumours in the brain are not of rare occurrence in the horse, although they are very limited in variety. Moreover, they are seldom found to exist save in the lateral ventricles or cavities within the hemispheres. They are almost invariably of that variety termed " psammoma", a structure comprising a quantity of fibrous tissue, in the mesh-work of which are found granules of earthy matter, fatty particles, and thin glistening plates of cholesterine. These tumours are developed in the fringe of vascular membrane, termed the "choroid plexus", which is situated on the floor of the lateral ventricles. They vary in size from a pin's head to a hen's egg, and frequently occur in both ventricular cavities. Being slow in their growth they seldom produce any obvious disturbance in the conduct of the animal until they have reached considerable dimensions, although in the course of their development the venti'icles become much dilated, and a consider- able amount of brain matter is caused to be absorbed by the pressure which they make upon it. They are usually ovoid in form,, of a bluey- gray appearance, smooth on the surface, and firm to the touch. Brain tumours in the horse are mostly found in the adult and later periods of life, although the writer has removed them from the ventricles of so young a horse as a four-year-old. Cause. — As to the origin of these formations, nothing definite can be said; inasmuch, however, as they are more prevalent in harness horses than others of the riding class, it has been suggested that the pressure of tight, ill-fitting collars on the jugular veins may, by interrupting the circulation from the brain, be the means of causing their development, and it is very likely this may be a predisposing or even an exciting cause. Symptoms. — The symptoms developed as the result of the continued growth of these formations may be of a chronic or an acute and fatal character. In the former the animal suffers periodic attacks of loss of power and unconsciousness for some time, the intervals between each attack becoming shorter as time goes on, and the attacks more and more severe. They are specially excited when the horse is worked on a full stomach, or urged 416 HEALTH AND DISEASE too freely uphill when the pressure of the collar is increased, or driven in face of a hot sun. The frequent occurrence of these symptoms in the early spring and during the summer is mainly on account of exposure to the last-named cause. The attack comes on without warning. The animal stops and suddenly falls to the ground, the muscles quiver or are rigidly set, the eyes roll, there is loss of consciousness, and for a time also of feeling and muscular power. After a brief period the stricken beast regains his lost powers and is able to rise, but for several days he remains dull, feeble, and stupid, and altogether unfitted for work. In other cases the animal hangs his head, and presents an expression of drowsiness and an indisposition to move. In less severe attacks he will suddenly stop while being driven, lay back his ears, shake his head violently, or throw it up and down without any obvious reason, and in a few minutes resume his journey as if nothing had happened. In the more severe attacks the patient is stricken down paralysed and unconscious and quickly succumbs. Treatment in these cases is of no avail, and although something may be done to ward oft' the attacks by a judicious system of general manage- ment and feeding, horses affected with brain tumours are dangerous beasts to possess, and should be destroyed. CEDEMA OF THE CHOROID PLEXUS This is a condition in which the choroid plexuses of the ventricles are infiltrated with fluid which has escaped from the fine net-work of veins of which they are mainly composed. So far as is known it is of somewhat rare occurrence. It may, however, be more common than is generally supposed, were post-mortem examinations more frequently made of the brain in those cases where death foUow^s upon sudden and complete coma. The causes of oedema of the choroid plexuses is not well established, but in the case of which an illustration is here given (see Coloured Plate) the horse had been the subject of influenza, and appeared to be making a good recovery. He was, however, suddenly seized with dulness, followed by deep coma, and death occurred twenty-four hours later. Post-mortem examination showed clots of coagulated blood obstructing the veins leading from the plexuses into the veins of Galen. There was nothing either in the history of the case, or in the post- mortem inspection, to show why the blood should have clotted and obstructed the circulation in these veins. A blow on the head in such DISEASES OF THE NERVOUS SYSTEM 417 circumstances might have caused it, or it may have resulted from some ciiaiige in the blood consequent on the disease. Where, as in this instance, the choroid plexuses were torn up, treat- ment could be of little avail. EXOSTOSES OR BONE TUMOURS Hard ivory-like growths from the petrous temporal bone sometimes extend into the cavity of the cranium and occasion pressure upon and absorption of the brain substance. These tumours, developing very slowly, afford the neighbouring parts an opportunity to accommodate themselves for a time to the altered state, but sooner or later the pressure they impart to nerves and vessels produces various forms of structural and functional derangement, among which may be mentioned deafness, paralysis of the muscles of the face, loss of motor power, unsteady movements, convulsive fits, followed by apoplexy and death. Exostoses or bone tumours sometimes occur on the floor of the cranium as the result of a Ijlow on the poll or back of the head, such as would be inflicted by a horse falling backward or striking the head violently against some fixed object. In these cases blindness may follow as a con- sequence, from pressure on the optic nerves at their bifurcation; or the muscles of the eye may suffer paralysis, and disorders of some of the other nerves issuing from the base of the brain may result. THICKENING OF THE MEMBRANES Professor Williams, in his Principles and Practice of Veteriiicu-y Mediciiie, refers to a case in which the dura mater or outermost covering of the brain attained a thickness varying from one inch at the base to several inches at the anterior part of the cranium, causing absorption of the frontal and ethmoid bones, and closing the frontal sinuses. The hoi'se in which this was discovered had presented signs of brain disease, sleepiness, partial paralysis, blindness, and paralysis of the muscles of mastication for a considerable period before its death. " It is very probable". Professor Williams remarks, " that this condition was the result of an injury, such as a blow upon the head, causing chronic inflammation." 418 HEALTH AUD DISEASE DISEASES OF THE SPINAL CORD AND ITS MEMBRANES ACUTE SPINAL MENINGITIS— INFLAMMATION OF THE MEMBRANES OF THE SPINAL CORD Acute inflammation of the coverings of the spinal cord is of seldom occurrence, and mostly involves the two innermost membranes — the pia mater and ai-achnoid. The causes which give rise to this disease are for the most part the result of injury, but it may also follow upon exposure to cold easterly winds and wet, especially in the case of a horse that is heated after a fast run with hounds and much jumping, or after a period of heavy draught. Tumours in the spinal canal, and the bursting of abscesses into it from disease of the vertebrae, may also occasion it. Symptoms. — These will vary in severity, according to the intensity of the cause. They may either be sudden and severe in their onset or slowly progressive. In the former case the disease is ushered in by rigors or shivering, followed by paroxysms of pain in the course of the spine, exhibited more especially when the animal is made to move. Later, sudden and repeated fits of spasmodic contraction of the muscles of the limbs appear, causing them to be suddenly jerked upward and forcibly brought to the ground. The movements become unsteady and the fet- locks knuckle over, the patient loses the power to stand, and sooner or later becomes completely paralysed. When on the ground he makes repeated attempts to rise, during which there are violent fits of struggling and painful spasms of the muscles of the limbs and back. During these paroxysms the face wears a drawn and anxious expres- sion, deep groans are emitted, the breathing becomes hurried, the pulse quickened, and sweat covers the body. Short intervals of ease follow the convulsive seizures, but growing muscular weakness, followed by complete paralysis of both motion and sensation, sooner or later ends in disablement or death. ACUTE MYELITIS— INFLAMMATION OF THE SPINAL CORD The causes which give rise to inflammation of the membranes of the cord are also responsible for inflammation of the cord itself, and mostly affect both structures in varying degrees at the same time. Symptoms. — At the onset of the disease more or less stiffness is ob- .served in the spine. The animal, when made to turn, does so in a wide circle. Firm pressure over the spine occasions pain. The hind-limbs are PARALYSIS 419 rept.'atiHll}- moved and sometinios .strike the ground, or tliey are sliakcn as if to detach something objectionable adhering to them. SensibiUty becomes diminished, and a rolling movement behind is observed when the animal attempts to walk. Muscular paralysis of the parts behind the seat of disease soon follows, and the patient falls to the ground unable to rise. The bladder now may fail to empty itself and become distended with urine. The fteces escape involuntarily in consecjuence of paralysis of the muscle (sphincter ani) which closes the anus. The bowels are con- stipated, but there is little, if any, rise of the bodily temperature. The farther forward the disease exists in the cord the more extensive will be the paralysis. When in the region of the neck the fore-limbs as well as the hind will become disabled, and the muscles of respiration will at the same time be involved, and occasion great difficulty of breathing and more or less disturbance in the action of the heart. These affections of the spinal cord and its membranes usually, become complicated with some rapidly destructive lung disease, or with inflamma- tion of the bladder or kidney disease, to which the victim sooner or later succumbs. Should he escape these immediately fatal afl'ections he remains paralysed and useless. Little, therefore, is to be expected from treatment of an animal so aftected, and both humanity and economy will be best served by his immediate destruction. PARALYSIS By paralysis is understood a loss of power in the muscles to contract, and consequently greater or less impairment of voluntary motion. There is also a second form of paralysis, by which a part may be deprived of the sense of feeling. The former constitutes paralysis of motion, the latter paralysis of sensation. They frequently occur together, but when this is .so the loss of power usually exceeds that of sensation. Each may exist alone. The more common of the two as separate ailments is paralysis of motion. Paralysis is not a disease, but a symptom of some disorder going on either in the brain or spinal cord, or the nerves connecting them with the paralysed part. If for any reason the brain fails to develop and to give out voluntary impulses, the influence of the will ceases to act upon those parts over which it ordinarily exercises control. The nerves, although healthy in themselves, receiving no nervous force from the aff"ected centre, become incapable of exciting muscles to contract. On the other hand, the brain or nerve centre may be perfectly free from disease, but owing to some pressure or disease in the course of the nerves 420 HEALTH AND DISEASE the impulses developed by the healthy brain fail to travel along the dis- eased nerves, with the result that paralysis ensues in the part to which they are distributed. The nerve centres and the nerves are liable to become disabled from a number of diverse causes. Lack of nourishment, the consequence of in- sufficient blood supply; certain poisons introduced from without or formed within the body, such as lead or the accumulation of urinary or biliary pro- duets in the blood; mechanical injury or pressure; rupture of blood-vessels in or upon the brain; the formation of tumours; inflammation and its con- sequences, are all found to produce paralysis at one time or another. From what has been stated it will be seen that paralysis may originate — (l) in the brain (cerebral), (2) in the spinal cord (spinal), (3) in the nerves con- nected with the one or the other (peripheral paralysis). Hence it follows that the disease presents a considerable variety of forms, of which onlv those of the more common kind will be considered here. HEMIPLEGIA In this form of paralysis one lateral half, the right or the left side of the body, is involved. It is a rare affection in the horse, but in man it is one of the most common forms of the disease, and usually appears suddenly in what is commonly known as a " stroke ". The jDarts affected in hemi- plegia are the fore and hind extremity, the muscles of the face, especially those of mastication, and the tongue on one side. The loss of power may either be complete or incomplete, according to the intensity and extent of the cause, which commonly arises out of rupture of the vessels of the brain, with more or less escape of blood into the tissues of the organ. Symptoms. — Hemiplegia is usually sudden in its onset. The affected animal falls to the ground in a more or less unconscious condition, and the limbs on the paralysed side are incapalile of movement. In a case quoted from M. Gerard by Percival the sensibility of the left, the affected side, proved extremely acute. The lips and alse of the nose were drawn to the right side, the contrary to that to which the head and neck turned. A blowing noise was made by the air in its passage through the nostrils. The left ear was paralysed and the tongue distorted. When oats were laid before the horse it seized them with the right side of the mouth, the left remaining motionless. There was great difficulty in masti- cation, and some of the food was not swallowed, but became lodged between the cheek and the molar teeth. In feeding, the horse plunged its muzzle into the middle of its food and opened its mouth wide. In drinking, PARALYSIS 421 its inoulh was thrust deeply into the water. It could walk, hut ouuld hardly sustain itself after but a short exercise. (.)n the fourth day the animal was unable to stand, sank down, and after several ineffectual struggles to rise, rolled over and lay upon its right side. Its pulse and respiration remained undisturbed. It died on the seventh day. PARAPLEGIA— SPINAL PARALYSIS Paraplegia indicates some disorder of the spinal cord, and consists of paralysis of the posterior half (more or less) of the body. The extent of the disablement will depend upon the seat of the disease, being greater in proportion as it is situated in a forward direction. Injury affecting the spinal cord in the region of the back or loins would paralyse the hind- quarters equally or unequally, but if it occurred in the neck, the fore and the hind limbs also, and the rest of the trunk behind the damaged cord, would also be deprived of the power of motion. Paraplegia in the horse is most commonly the result of injury inflicted on the dorsal or lumbar portion of the cord or its membranes, as when from some cause the latter become thickened and unduly press upon the former, or when they contain large quantities of fluid as the result of injury. Bony growths projecting inwards from the spine sometimes press upon the cord and cause paralysis, or the same results may follow dislocation of the vertebrae. Rarely spinal paralysis is due to causes originating in organs cjuite away from the spine, as when mares sufi'er during oestrum, or foals in consequence of worms in the bowels. This is termed " reflex paralysis", a form of the disease from which animals affected frequently recover. Here uterine irritation in the one case, and intestinal irritation in the other, is the cause of the failure of the spinal cord to innervate the muscles. Symptoms. — In paraplegia there is more or less complete paralysis of the hind-quarters. When it is complete the animal occupies a re- cumbent posture and is unable to rise. When the skin of the paralysed region is pricked with a pin there is usually no sign of feeling, but in some instances the paralysis may be almost exclusively that of motion, while sensation remains intact, in which case the prick will be felt and expressed by the animal's movements in front. The urine may be dis- charged involuntarily, and the feeces too may escape in consequence of paralysis of the sphincter ani. In incomplete paraplegia the hind-quarters roll from side to side, the animal crosses his hind-limbs, sometimes trails the toes, or knuckles over 422 HEALTH AND DISEASE witli the fetlock joints. Movement aggravates the symptoms, and may cause the animal to fall, when more or less difficulty or complete inability will be experienced in rising. Paraplegia in the horse, save when arising out of reflex causes, offers very little encouragement to treatment. Injury to the brain or cord of a paralysing nature seldom yields to medicine. In cases of a slight character it may be desirable to administer a dose of physic, to apply hot cloths over the loins, and to place the animal in slings or on a good bed of peat-moss, and later to administer iodide of potassium and nux vomica for two or three weeks and apply a blister along the back; but these are cases which should be promptly placed under the care of a qualified person. PERIPHERAL OR LOCAL PARALYSIS When paralysis is confined to muscles supplied by a pai-ticular nerve it is said to be " peripheral ". The most common example of this form of the malady is that in which the seventh nerve is involved. The seventh nerve after leaving the brain emerges from the cranium through a canal in the Kg. 180.— Facial Paralysis, a, Partial. B, Total. petrous temporal bone, and on reaching the surface passes underneath the joint fonmed by the lower jaw and the temporal bone, and then over the cheek, where it gives off branches to the muscles of mastication, the nostrils, and the lips. Injury to this nerve gives rise to paralysis of the muscles of the face, hence it is termed " facial paralysis ". It may occur on one side, as is mostly the case, or both nerves may be simultaneously affected. Causes. — Facial paralysis may result from injury to the nerve as it CEREBROSPINAL MENINGITIS 423 passes throuoli the canal in the tiMiiporal hone. Tliis may he the result of disease of that hone, or of some effusion into the sheath of the nerve from inflammatory conditions. Injury to the nerve after leaving the canal is the more common cause, such as blows beneath the ear when rolling, or being cast, or from other causes. Pressure from tumours or abscesses, or inflannnatory swelling in its ((nirsr, will also produce it. Symptoms. — Where a nerve is paralysed the angle of the mouth on the sound side is drawn upward, while that on the paralysed side is lowered. The lips hang loose and pendulous, the eye cannot be closed, the nostril of the affected side cannot be dilated, the cheek is flaccid and has lost its firmness to the touch. In feeding, the patient seizes his food with the teeth instead of gathering it up with his lips. In drinking, the mouth is pushed into the water for some distance, and during mastication food falls from the mouth on the paralysed side. Treatment. — When due to abscess or inflammatory swelling hot fomentations and poultices should be apjjlied to the affected part. If possible the abscess should be laid open and emptied, so as to remove the pressure on the nerve. This should be followed by iron tonics and nux vomica to restore the lost power to the muscles, and, if necessary, the application and repetition of iodine blisters. Where a tumour or intlam- matory swelling exists, a purgative followed by iodide of potassium in full doses should be given. CEREBRO-SPINAL MENINGITIS A fatal affection among horses implicating the spinal and cerebral membranes appears to have been known for a long period in various parts of the world. In the United States of America cerebro-spinal meningitis is recorded to have been investigated in 1850. In Germany it was known in 1865, and in Egypt ten years later. About the year 1881 a fatal form of paralysis attracted notice in this country, and Professor Axe described outbreaks which occurred almost simultaneously in Essex, Loudon, and Norfolk. A peculiarity of the disease at the time was its limitation to certain parts of the year, the majority of cases occurring between the end of February and the beginning of May. Mares seemed to be more sus- ceptible to the affection than horses, and animals of all ages were attacked. Climatic conditions did not appear to have any marked influence on the progress of the malady. When it was first recognized in 1881 the weather was cold and wet, but since then cases have been observed in the latter part of the summer dui-ing hot bright weather. 4-24 HEALTH AND DISEASE Ou the first appearance of the affection it was looked upon as a totally new malady which had probably been introduced from America. Percival in his Hip20O Pathology refers to a form of epizootic paralysis occurring on cold wet pastures in spring and autumn. Professor Axe mentions an article by Mr. Small in the Veterinarian for 1857 describing outbreaks of paralysis occurring in his district in that year. Other writers have also mentioned cases of the periodical occurrence of a form of paralysis in different parts of the country, and there is very little doubt that these cases were of the same character as those which have been recently designated cerebro-spinal meningitis. With regai'd to the propagation of the disorder Professor Axe notices the communication of the disease to other animals than the horse. On this part of the subject he says: — " At the time when the disorder prevailed in the county of Essex, Mr. Ellis, veterinary surgeon of Maldon, resolved upon trying the efficacy of venesection. Several horses were consequently bled, and the blood removed from them was, contrary to instructions, thrown down in a yard adjoining the stables. During the day large numbers of sparrows were observed to partake freely of the clot, and after a short period to become paralysed in their wings, and unable to rise from the ground. On the following day a sow and a dog, which had also consumed some of the blood, were similarly affected, the latter so much so as to lead to his destruction. Several young pigs, offspring of the sow referred to, were at the same time seized with convulsive twitchings of the voluntary muscles, accompanied by a greater or less degree of paralysis. These latter animals, it should be mentioned, had not partaken of the blood of the horse, but were at that time subsisting exclusively on the milk of the dam." Symptoms. — Indications of the disease in the majority of instances appear suddenly, but in other cases before there is any appearance of paralysis the animals show some premonitory signs of drowsiness, unsteadi- ness in their movements, catching the toe in the ground in walking. More commonly, however, without any warning the affected horse is found down and almost incapable of moving. In many cases the loss of power is apparent in the posterior half of the body, and during the progress of the affection nearly all the muscles of motion are involved. Sometimes the loss of power is particularly marked in muscles connected with swallowing, so that the animals cannot take fluid or solid; in other instances the power to eat and drink remains, while paralysis gradually extends over the body. In the advanced stages of the disease excitement is frequently pi-esent, alternating with spasmodic contraction of some of the muscles. The excitement mav be followed bv total loss of consciousness, or it may be I BEHJEA "vltl . " il r .! A. Portion of spin.il cord showing engorgement of vessels and h«;morrIiagic points and patclies in ccrebro-spinal meningitis. B. Arteritis.— Portion of aorta laid open, showing patches of arteritis. C. Arteritis. -Transverse section of artery infiltrated with inflammatory products, {a) Leucocytes in tunica adventitia or external coat, {b) Leucocytes infiltrating tunica media or middle coat. (<•) Leucocytes causing irregular thickening of tunica intima or internal coat. P. Arteritis. -Longitudinal section of inflamed artery. («) Leucocytes infiltrating vessel wall. THE ABSORBENT SYSTEM 495 exaggerated and end iu frenzy. These symptoms usually indicate that a fatal termination is at hand. During the course of the disease the temperature is but little affected, and, excepting when complications arise, the pulse and respiration are nearly normal. On post mortem examination it has been found that the membranes of the brain and spinal cord are charged with blood, and effused blood and serum are frequently found on the brain and spinal cord. The digestive and respiratory organs, and also tlie spleen and kidneys, show considerable changes in their texture. No satisfactory explanation has been given of the origin of the disease. It has been looked upon as infectious, and recent experience of the malady goes to prove pretty conclusively that it is so. The fact of its recurrence occasionally and under very different conditions is sufficient in itself to prove that it is not due to any of the ordinary causes. Whatever the cause may be, it is quite certain that it only exists at intervals, and also that it affects a considerable number of animals in the district in quick succession. The cessation of the disease is sometimes as sudden as its appearance. Treatment, — Of the different plans of treatment which have been tried none has proved so successful as to claim any pre-eminence. Laxa- tives, cold applications to the head, and in cases where muscular spasms in the neck, for example, are present, injections of morphine have been tried with partial success. For the prevention of the spreading of the affection it is desirable to remove healthy animals from the immediate neighbourhood of the sick. Efficient cleansing and disinfection of the stables in which sick horses have stood must on no account be neglected, and a complete change of food is also desirable. 5. THE ABSORBENT SYSTEM This important system is composed of two parts, of w^hich one is especially connected with the alimentary canal, whilst the other is widely distributed throughout the body. The former is named the lacteal system, the latter the lymphatic system. Both are composed of vessels presenting a general resemblance to those which convey the blood, and both ulti- mately discharge their contents into the thoracic duct, a tube which lies beneath the vertebral column and opens directly into the anterior vena cava. Both are interrupted in their course by glands — the lymphatic o-lands — of which those in relation with the lacteals are chiefly situated 426 HEALTH AND DISEASE iu the abdomeu at the root of the mesentery, whilst those connected with the lymphatics are found in the axilla, groin, neck, thorax, &c. The purpose of the lacteals, which have their origin in the intestine, is to absorb or take up the constituents of the food, in which they are assisted by the blood- vessels, whilst the lymphatics, which are everywhere distributed through the tissues of the body, reconduct to the larger blood- vessels the plasma of the blood which, having passed through the walls of the smaller blood- vessels, is in excess of the requirement of the tissues, and contains some of the products of their disintegration. As there are some dif- ferences between the lacteal and lymphatic vessels it will be expedient to describe them separately, though it must be borne in mind that they are only parts of the same system. The Lacteal System.— It is justifiable in common parlance to say, when an animal has eaten a hearty meal, that it has got its food inside it, but from a physiological point of view the food is still in reality outside tlie body, and no matter what quantity has been ingested it is unavailable for the nutri- tion of the tissues, or the production of heat or of nervo-muscular force, until it has been absorbed and assimilated. The starches, oils, and proteids which form the staple of the typical foods such as oats, barley, wheat, and other cereals are, in the raw state, in- capable of passing through the walls of the intestine. In order that they may do so it is necessary that they should be rendered solui)le, and this duty devolves on the various digestive secretions, that we have seen are poured forth from the numerous glands connected with the alimentary canal. By these juices starches are converted into sugars, oils into very fine emulsions or into soaps, and proteids into peptones, being in each case so modified that they are rendered capable of ])ermeating the intestinal walls and the vessels ramifying upon thcni, and thus truly entering Fig. 181.— Sketch of the Lymphatic Vessel; of the Fore-Leg (inner aspect) THE AHSOKliKNT SYSTEM 427 the body and bec-oiuiiig first assimilated to iuid then incoipoiated with it. The process by wliich the solutions of sugar, oil, proteids, or salts penetrate the wall of the alimentary tract is termed " osmosis ", and can easily be shown by immersing a bladder filled with thick syrup in a jar of pure water, when a double current is immediately established. Some of the sugar solution escapes into the surrounding water, whilst a much larger proportion of pure water passing through the membrane to the syrup enters the bladder, dis- tending it to the utmost and even to bursting. The lacteal system may be said to commence in the delicate velvet pile- like processes or villi which line the whole of the small intestine, and whicli are shown in the accompanying wood- cut (tig. 182, 1). Each villus contains a net-work of minute blood-vessels, not here de- picted, surrounding a vessel of larger size (2), which is the lacteal. The latter, commencing near the summit in a blind extremity or a loop, passes down to the base of the villus, where it joins with others to form a net- work. These, after meeting together, emerge from the intestine as vessels of con- siderable size (2, 2), which accompany the blood-vessels of the mesentery, and, gradually uniting to form larger and larger trunks, terminate beneath the spine in a kind of sac or bladder (receptaculum chyli) which represents the hinder end of the thoracic duct. Whilst still contained within the villi, the lacteals are surrounded by muscular fibres, and when these fibres contract, the villi are changed in form from long finger-like processes into short projections, and the fluid they have absorbed, to which the term chyle (Greek clwJos, juice) is applied, is consequently driven into the underlying net-work of vessels. The villi thus constitute small force-pumps which, though in- dividually feeble, yet as a result of their numbers become important agents in the onward movement of the lacteal fluid. The vessels forming the net-work are provided with valves in their course which do not allow any backward current, but compel the fluid absorbed to move on towards the Fig. 182. — Section through the Small Intestine ' Villi. ^ Lacteal Vessels. ' Muscular Coat. ■* Serous Coat. 428 HEALTH AND DISEASE receptacle into which it is to be poured. During fasting the lacteals only contain a clear fluid, and were on this account long overlooked. It is only after the consumption of oily foods or of some such fluid as milk that they present the white appearance which has led to the name of lacteals (Latin lac, milk) being applied to tliem. Although the lacteals are highly important agents in the absorption of the soluble constituents of the food, the part played by the blood- vessels which ramify on the wall of the alimentary canal must not be overlooked. In the lower Vertebrata, as in fishes, no lacteals exist, and therefore all materials absorbed must be taken up through the walls of the blood-vessels in these animals, while it is obvious that the presence of a swift current of a thick fluid like blood on one side of the vascular wall must constitute a favourable condition for the absorption of a thinner and more difl'usible fluid from the other side. The Lymphatic System. — This system commences in the skin, and in the little spaces between the elements of the tissues in almost all parts of the body. It can be easily demonstrated by means of injections, for if a needle with a fine bore be plunged into the skin or into the muscles, and mercury or warm solution of gelatine holding some colouring material in suspension, as vermilion or Prussian blue, be forced through it with syringe, a beautiful and very close net-work of channels comes into view, which is quite distinct from the blood - vessels, and has no direct communication with them. The minuter blood - vessels, although they come into very close relation with the cells of glands and the fibres of muscle, do not actually touch them. There is always a layer of fluid, named lymph, between the two, so that, separating the blood from the actual constituents of every tissue, there are the wall of the blood-vessel and the layer of lymph outside that wall, as well as the walls of the vessels in which the lymph is contained, which indeed consists only of very thin cells. It is in the irregular spaces that are thus formed that the lymphatics arise. The spaces thus lined by flat cells soon, instead of l)eing irregular, become tubular. The Lymphatic Glands. — These bodies may be likened to oval or rounded masses of sponge, into which the lacteals convey chyle and the lymphatics lymph. Fig. 183 represents the structure of one of these glands. The gland has an investing coat or capsule (7) which completely surrounds it. From the capsule fibrous .strands (6) pass into the gland, dividing it oft' like partitions into spaces. The spaces round the circumference (or cortex) of the gland are of considerable size, and are more or less oval (3), while the spaces towards the centre (or medulla) are irregular in shape, and thp: absorbent system 429 smaller. The spaces are almost eompletely tiJled with masses of material, consisting of a net-work of very delicate connective tissue, in which white cells (4) of various sizes are entangled. This sort of tissue is called " adenoid ", or gland tissue, from the Greek, adeen, a gland. But the masses of tissue do not quite till the spaces. Between the outer surface of the mass and the wall of the space are channels (5), and the channel round one mass communicates with that of another, and those round the edge communicate with those in the centre, so that the gland might be looked upon as a mass of gland tissue broken up into numerous little clumps by a series of irregularly winding and communicating channels. The channels, moreover, are not perfect fair-ways. They are crossed and recrossed by spans of the delicate tissue of the gland, so that the whole structure becomes not unlike that of a sponge. Now the lacteal vessels join the mes- enteric gland at the margin or outside (l), and pour their tiuid contents into the chan- nels there. From them the riuid filters its way to the channels of the centre, bath- ing and peneti'ating the gland tissue in its course, and finally joins other vessels (2), l)y which it is carried away from the gland. Through these comparatively free channels the chyle or lymph makes its way, easily entering the gland by the afferent, and escaping by the efferent vessels, and it then carries away frorn the gland but few leucocytes. AVhen, however, the pressure of the fluid entering the gland is augmented, either by the process of digestion and the contraction of the villi in the case of the lacteals, or by active muscular movements in the case of the lymphatics, the lymph then per- colates the substance of the gland and carries ofi" with it by the efferent vessels large numbers of white cells, which are swiftly poured into the blood, and are believed to constitute one of the sources from which the blood corpuscles are recruited. The main agents in eflfecting the movement of the lymph along its vessels are: (l) The force of the heart, which drives the plasma through the walls of the blood-vessels into the tissues; (2) the muscular move- ments of the body, generally aided by the valves present in all Ivmphatic Fig. 183. — Section of Lymph.itio Gland ((lia£rrammatic) ' Afferent Lymph Vessel. ' Efferent Lymph Vessel. ^ Cor- tical Substance. * Lymphatic Tissue. * Lymph Path. ^ Trabeculse sent in from ^ Fibrous Capsule. 430 HEALTH AND DISEASE vessels and the minute muscles surrounding the lacteals in the vdli. The pressure under which the lymph moves is very low, and it is dis- charged from the thoracic duct into that part of the blood vascular system where the pressure is lowest, namely, into the veins just before their entry into the right auricle of the heart. When the outward movement of the lymph towards this point is impeded it accumulates in the vessels beyond the obstruction. This condition is more marked, and appears earlier if the obstruction be of such a nature as to affect the venous system as well as the lymphatic. The conditions known as oedema and drojjsy are then established. The composition of the lymph is very similar to that of the plasma of the blood, but it contains more water and less proteid matter. In the case of the horse there are about ninety-five to ninety-six per cent of water, and four or five per cent of solids, of which about three parts are albuminous or proteid substances, the remainder consisting of salts, the most abundant of which is common salt or sodium chloride. The composition of chyle, consisting chiefly of the digested materials contained in the alimentary canal, varies with the nature of the food and the period of digestion at which it is examined. In the fasting animal it does not differ materially from the lymph, but, with an oily diet like milk, the proportion of fat undergoes great increase, and the lacteals become conspicuous by their white colour. After passing through the lymphatic glands, the lymph and chyle alike acquire the power of coagulating or clotting, though in both instances the clot is feeble and soft. 6. THE ORGAI^S OF CmCULATIOK THE BLOOD From the earliest ages the blood has been held to be one of the most important constituents of the body, for it was natural, when death was seen to follow alike in animals and in man the infliction of a small wound {j)roviding it opened a large vessel), to believe that as the blood drained away, the life itself was leaving the body. The practice of strict Jews of all periods of their history, acting up to the command: " But flesh, with the life thereof, which is the blood thereof, shall ye not eat ", is evidence of the strong impress the constant association of loss of blood and of life has made on the mind of man. In many points of view it is indeed the river of life, for its flow sup])lies to all parts of the ])ody the materials requisite for their TllK BLOOD devi-lopiiKMit, niainlcnuiii'i', ami ici)air, whilst it is in addition cJiargud witli the vivifying oxygen it has absorbed at the hnigs. On the other hand, it carries away from eaeli part the prodncts of disintegration and decay, and condncts them to the organs by which they may be severally eliminated from the system, the most important being the carbon dioxide, which is discharged at the lungs, and the urea, which is excreted or thrown oti" by the kidneys. The blood of the liurse, like that of other mammals, is of a deep-red colour, but brighter in the arteries than in the veins. The taste is mawkish, tlie odour faint but peculiar, and its reaction to test-paper invariably alka- line. Its specific gravity is about 1-OGl. It is clammy or slippery to tlie touch, and is remark- ably opaque, transmitting liut little light even in thin layers. It is in con- stant movement in the body. The quantity of the blood contained in a horse of average size is estimated to be about one- eighteenth of its body weight, or from 40 to 45 lbs., and it is con- sidered that one-fourth is contiiined in the heart and larger blood-vessels, one- fourth in the muscles, one-fourth in the liver and intestines, and the remaining fourth in the other organs of the body. To the unassisted eye, the blood as it issues from a wound appears to be perfectly homo- geneous, but when examined with a microscope of moderate power it is seen to be composed of a transparent fluid named the 'plasma, in which are suspended a large number of corpnacles (fig. 184). The existence of corpuscles in blood was first noticed in the hedgehog by the celebrated Italian physician and anatomist Malpighi in the year 1661, who thought they were globules of fat. They had previously been seen, in 1658, by the Dutch anatomist Swammerdam in the frog, but this investigator lost the credit of the discovery in consequence of his failing to publish his observations. The real merit of recognizing the corpuscles as constant and essential elements of the blood is due to another Dutch microscopist named Leeuwenhoek, who in 1673 observed and described them in man and many other animals. Great attention has been bestowed u]ion them E F B C Fig. 184.— Blood Corpuscles A, Coloured Blood Corpuscles adhering together in Columns (rouleaux). B, Coloured Corpuscle, showing concave surface, c, The s;ime seen edgewise. D, E, F, Colourless Corpuscles. 432 HEALTH AND DISEASE by numerous observers, and three chief fonn.s of corpuscles have been distinguished, named, respectively, red corpuscles, white corpuscles, and blood platelets. The red corpuscles are pale-yellow circular discs, each resembling a coin, with edges thicker than the central part, and they are hence said to be biconcave. Their consistence is like that of moderately firm jelly. They have no nucleus. The transverse diameter is about -g-^oo inch, and their thickness about ^oooo i"ch. They are a little heavier than the fluid in which they are suspended, and consequently have a tendency to fall to the bottom of the vessel when blood is removed from the body. This disposition to gravitate may be observed in the living animal, since if blood be gently drawn with a small syringe from the upper and lower parts of a large horizontal vein — like the external jugular or neck vein when the animal is recumbent — the number of the corpuscles contained in the specimen taken from the lower part of the vein will be found to be much greater than in the specimen taken from the upper part. The number of the corpuscles in the body of a horse is inconceivablv great, but they may be counted in small quantities of blood which have been diluted with water, and it has been ascertained that there are no less than five or six millions in a cube -^ inch on the side, which would be represented by a very small drop. In e^'ery hundred parts of the red corpuscles there are about seventy parts of water and thirty parts of solids, and if the solids be examined after the water has been evaporated, every hundred parts are found to consist of eighty-eight parts of haemoglobin, ten parts of proteid substance of the nature of globulin, and two parts of lecithin and cholesterin. The haemoglobin then is the most abundant, as it is the most important, constituent of the blood. It is to it that the blood owes its colour, and it possesses several remarkable properties. In the first place, it is one of the prime factors in the process of respiration, being the carrier of oxygen between the air and the tissues, combining with this gas in the lungs, but holding it with so weak a grasp as to surrender it to the tissues during the brief period that it is in proximity with them whilst traversing the more minute or capillary vessels. It is possible, although it has not as yet been proved, that haemoglobin presents similar relations with carbon dioxide, taking up that gas in the tissues, in exchange for the oxj'gen with which it parts, and permitting its escape at the lungs in exchange for the oxygen it there absorbs. In this case it would serve as a carrier for both oxygen and carbon dioxide, its relations to each gas being governed by the degree of chemical affinity between the haemoglobin and the gas and by the tension of the gas at the moment of exposure to it. Experiment has shown that every ten grains of haemoglobin is able to TllK BLOOD 433 al).soib about a cubic iiicli of oxygen ga.s. Its relation to (carbon dioxide is less accurately known. Another peculiarity of hgemogiobin is its capa- bility of forming crysttds (fig. 185), some of the forms of which are here shown. The shape of these crystals in the horse is prismatic, as is usual in mammals. They are soluble in water. When by various means, such as freezing and again thawing, or by tlie addition of a little chloroform or ether to fresh blood, the haemoglobin is rendered soluble in the plasma, the blood retains its colour, but becomes transparent like port wine. It is then named laky blood. The chemical composition of haemoglobin is extra- ordinarily complex, one of the latest observers giving; the formula — rig. ] 85. —crystals of Hajmogiohin Carbon. Hydrogen. Nitrogen. 0.\ygen. Iro n and Salts. 712 1130 214 2-4.5 2 The coloured corpuscles of the blood are constantly undergoing destruc- tion, whilst new ones take the place of those that disappear. If such a renewal did not occur, every large loss of blood would inflict permanent injury on the animal, whereas experience shows that recovery soon takes place, even from abundant hemorrhage, temporary weakness being followed by perfect restoration to health and strength. As much as a gallon of blood may be withdrawn from the veins of a horse every month for several months together without impairing its health. The seats of formation, or the factories as they may be called, of the coloured corpuscles, appear to be the absorbent glands and their tributaries; the cancellous or spongy tissue in the heads of the long bones; the liver; spleen; thymus and thyroid bodies, and the gland-like tissue forming the sub-mucous coat of the alimentary canal. This difference in their place of origin may account for minor differences observed in the size, form, and colour of both the red and the white corpuscles. As the red corpuscles grow old they seem to enlarge, to lose their coloured contents, and either to break up in the vessels or to be seized upon in the spleen or other organ and consumed b}- large colourless cells named phagocytes. Additional reasons for believing that their term of life is not a long one are, first, because great numbers of colourless corpuscles, some of whic-h become coloured, are added to the blood after every meal; and, secondly, because if the blood of one animal be injected into the vessels of another. 434 HEALTH AND DISEASE tlie corpuscles, if capable of being distinguished, do not long persist in their new host. The white or colourless corpuscles, named also leucocytes and lympho- cytes, are present in the blood in much smaller number than the red. The proportion that they have to each other is not, however, a constant one, owing to the fact just stated, that a large accession to the numbers of the white corpuscles occurs after every meal. In the fasting state there is about one white corpuscle to every fifteen hundred red corpuscles, whilst after food the proportion may rise to one white to three hundred red, or even higher. Perhaps, taking the average, the proportion is about 1:500 or 1:1000. The white corpuscles are spheroidal in form, dotted or granular in aspect, the granules they contain being in some instances coarse, in others fine, indicating in all pro- bability a difference in their place of ori- gin. By the action of various chemical substances a nucleus is brought into view, and sometimes two or three appear with great distinctness. Their diameter is Their most remarkable character is the power they possess of undergoing changes of form and of moving from place to place (fig. 186). They act, in fact, as if they were parasites, living in the blood, but not necessarily confined to that medium. If a drop of blood be received upon the warmed stage of a microscope, and evaporation be prevented, they may be seen to exhibit perfectly independent move- ments, thrusting out little processes in this or that direction and with- drawing them again, exactly as an amcsba would do if placed under the same conditions. By this means they are able to pass through the walls of the smaller blood-vessels and then wander freely through the outlving tissues, a process that is termed diapedesis. The small corpuscles known as platelets are flattened, disc-shaped, or irregular particles, in regard to the nature of \\liich little has been ascer- tained. The plasma of the blood, in which the corpuscles are susjjended, is a clear fluid having a specific gravity a little less than that of the corpuscles, which, therefore, when the blood is at rest, have a tendencv to fall to the "-v--^ Fig^. 186. — Colourless Blood Corpuscles, showiug successive chang driring a period of ten minutes about inch. THE Bl.OOD 435 bottom of the vessel. It contains a large proportion of nutritive material in the form of albuminous eonstituents, amongst which fibrinogen, serum- globulin, and serum-albumin are the most important, and it is also the solvent of many other bodies on their way to the tissues, or which result from the decay and disintegration of the various organs. Thus sugar, fats, urea, uric and hippuric acids, cholesterin and lecithin, and many salts are constant constituents. The following table shows the results obtained from the analysis of the blood-plasma of the horse by two excel- lent chemists, No. I being the result obtained by Professor Hoppe Seyler and No. II that of Professor Hammarsten. Hoppe Seyler only examined the blood- plasma of one horse; Professor Hammarsten of three, of which he took the mean. No. I. No. II. Water 9084 917-6 Solids 91-tJ 8L>-4 Total albuminous bodies ... ... 776 695 Fibrin 101 6-5 Globulin — 38-4 Serum albumin ... ... ... — 24'6 Fat 12^ Extractives ... ... ... ... ^ l lo.q Soluble salts .. . ... ... ... 6-4 j Insoluble salts ... ... ... 1"7.' The Coagulation of the Blood. — When the blood is withdrawn from the body, it sets, coagulates, or clots, becoming converted from a Huid into a jelly. This process occasionally occurs in disease, whilst the blood is still contained within the vessels. It takes place in different animals with various degrees of rapidity; thus in the blood of birds less than a minute .suffices to complete the change, while a quarter of an hour or twenty minutes may elap.se before the blood of the horse becomes a solid mass. Violent muscular efforts made by the animal before the blood is drawn, or the rapid cooling of the blood, eft'ected by surrounding the vessel into which it is drawn with ice, retard coagulation almost indefinitely. If the process of coagulation be carefully watched, it will be seen that on account of the corpusc'.es being heavier than the plasma, they sink through that fluid, their descent being aided by their disposition to adhere together by their broad surfaces, forming rouleaux (see fig. 181), and so presenting their edges to the fluid. The white corpuscles, though heavier than the plasma, are lighter than the red, and hence form a thin layer on the surface of the latter, the whole being surmounted by a moderately thick layer of plasma. Whether this separation of blood into layers have taken place or no, the whole mass becomes first vi.scous and then .solid, the difl'erence resemblinai; 436 HEALTH AND DISEASE that seen in the white of egg before and after boiling, or in gelatine before and after setting. The consistence of the clot is about equal to that of red- currant jelly. After the lapse of a few minutes a further change may be seen. The clot contracts, and minute drops of a clear fluid begin to exude from the surface. This is the separation of the serum from the clot; and, as the contraction continues for many hours, the clot is ultimately covered and surrounded by a layer of clear fluid of considerable depth. When the separation of the freshly-drawn blood into three layers has taken place, the contraction of the upper layer of plasma, being unhindered by the presence of corpuscles, causes the upper surface to be much depressed in the centre, and its colour being yellowish, such clot is spoken of as being " buffed and cupped ". It is, of course, not observed when clotting has taken place too quickly for the corpuscles to sink through the plasma. Coagulation of the blood is believed to result from the breaking up into two parts of a proteid substance named fibrinogen, naturally existing in solution in the plasma. One of these parts is a globulin which, under the influence of a ferment existing in the white corpuscles, remains in solution; the other is fibrin, which immediately solidifies, forming a delicate net-work in the meshes of which the corpuscles are entangled, and which, subsequently contracting, squeezes out the serum. The calcium salts also play an important part in the process. THE MECHANISM OF THE CIRCULATION The blood, the characters of which have just been considered, circulates through the body by the agency of the heart and blood-vessels. The heart is a portion of the vascular system, consisting of a compact but hollow mass of muscle that acts rhythmically as a pump, and, owing to the presence of valves suitably placed, drives the blood in one constant direction through the body. It is placed in the thorax or chest, and is protected from injury by the breast-bone and the firm but elastic ribs and spine, and also owing to its being enveloped to a large extent by the spongy tissue of the lungs. It is enclosed in a tough membranous bag named the j^ericardium, lined internally by a serous membrane, the smooth and polished surfaces of which, moistened with the fluid they secrete, reduce friction to a minimum. The general course pursued by the blood is from the heart, through the arteries and their ramifications, named capillaries, onward to the veins, by which it is again conducted to the heart. Although in appearance single, the heart is really a double organ, the two parts being united for the sake of economy of space and materia], and also to enable them to work eqaalily and simultaneously. THE MECHANISM OF THE CIRCULATION 437 One of the.se hearts, the riglit, forces the blood through tlie puhiionary artery to the lungs, from whence, by the pulmonary veins, it returns to the left heart. The right heart is therefore called the pulmonary heart, and is the effective agent in the lesser or pulmonary circulation. The left heart is by far the stronger of the two hearts, and drives the blood through the aorta and its branches over the system at large, from whence it is returned to the light heart by two large veins (venpe cavse). ■ Hence 138 HEALTH AND DISEASE it has been named the systemic heart, and is the main agent in effecting the greater or systemic circulation. The right heart forces dark or venous blood, charged with carbon dioxide, through the iungs, where, becoming aerated by losing that gas and absorbing oxygen, it returns to the left heart as bright or arterial blood, and is distributed to the body generally. The heart as a whole weighs about 7 lbs. Its length is about 10 inches, and its width at the base about 7 or 8 inches. It is of conical form, the base being directed to the spine. The capacity of each cavity is estimated to be about 1|- pint. The heart is composed of a form of muscular tissue intermediate between the striated and unstriated. The Figs. 1S9 and 190. — Diagrammatic Views of tlie Heart, showing Valves open and closed A, Pulmonary Artery. B, Posterior Vena Cava. c. Anterior Vena Cava. R.A., Right Auricle. * Auriculo- Ventricular Opening (open in the first figure and closed in the second). B.v. , Right Ventricle. » ■ Course of Blood. S.V., Semilunar Valves (closed in the first figure, open in the second). external or superficial layers run obliquely over both ventricles; the inner or deeper layers are confined to the right and left ventricles respectively. Each heart presents two cavities, an upper one, named the auricle, and a lower one, named the ventricle; so that there are two auricles and two ventricles, or four cavities in all. The right auricle receives the two vense cavse or large systemic veins above, and opens by a wide orifice into the right ventricle below, the aperture being guai'ded by the tricuspid valve. From the upper part of the right ventricle the pul- monary artery arises, the orifice of which is also guarded by the three semilunar valves. A similar arrangement exists on the left side. The pulmonary veins have no valves. They open into the left auricle above, and this communicates by a large orifice, guarded by the bicuspid valve, with the left ventricle below. From tlie left ventricle arises the aorta, THE MKCHAXISM OF THF CIRCULATION 439 the (M'iHcc of whicli i.s ulso guarded by three semilunar or .sigmoid valves. The heart of the horse heats in health about forty times in the minute. Tlie order of sueeession in the contraction is that the two auricles beat simultiineously, and then the two ventricles. Then there is a pause. The duration of the contraction is nearly the same as the pause. The con- traction of the heart is named the systole. During the systole the whole heart becomes shorter and more conical in form, and twists a little upon its long axis towards the right. This contraction of the heart commences above at the opening of the great veins, which, being here surrounded by muscular bands, nearly close, and thus greatly impede, but do not altogether prevent, the backward flow of the blood from the heart into the venous system. From the great veins a wave of con- traction instantly spreads over the auricles, driving the blood they contain through the auriculo- ventricular valves into the ven- tricles, which, already containing a little blood that has gravitated into them, are now distended to the utmost. There is no appreci able interval between the contrac- tion of the auricles and that of the ventricles, but the w^ave of contraction continuing, without stay or stop, to spread from the auricles, makes the ventricles close upon their contents. The first eflect of this is to raise the auriculo-ventricular valves and approximate their edges, and thus to prevent any return of blood into the auricles. The next is to propel the blood contained by the ventricles into the pulmonary artery and the aorta, for distribution through the lungs in the one case and over the general system in the other. In so doing the blood forces open the semilunar and sigmoid valves in these vessels and compels the whole mass of blood to move onwards. But as the column of blood resting on the valves just before they are forced open is quiescent, a brief period is required to overcome its inertia, and a remarkable provision against the jar that would otherwise be felt through the l)ody, from the \'igour and suddenness of the heart's systole, is found in the elasticity of the coats of the large vessels. Whilst, then, a jtart of tlic heart's force drives the Fig. 191. -Section of the Heart, showing the Valvular Apparatus B, Pulmonary Artery. D, Tricuspid Valv c. Mitral Valve. 440 HliALTH AND DISEASE blood forwards, a part is expended in dilating the arteries. As soon as the contraction is completed, relaxation immediately follows, and the heart passes into the state of commencing dilatation. The great vessels into which the blood has been forced now retract, and the first effect is to close the semilunar valves, and thus to prevent the return of the blood into the ventricles, whilst the next is to compel the onward move- ment of the blood in the vessels; the elastic reaction of the stretched walls restoring to the circulation during the diastole the force temporarily borrowed from the heart. The wave which is produced by the injection of blood into the vessels when the heart contracts is the pulse, but the closure of the semilunar valves is so sudden, and follows so immediately upon the contraction, that a reflex wave from the valves succeeds the main systolic wave and forms a part of the pulse. This is known as the dicrotic wave. If the ear be applied to the chest two sounds may be heard to accom- pany the action of the heart; the first is dull and prolonged, the second is shorter, sharper, and ends abruptly. The first sound owes its origin mainly to the sudden tension of the auriculo- ventricular valves in the right and left hearts, but is almost certainly intensified by the muscular sound of the contracting ventricles. The second sound is exclusively due to the sudden tension of the aortic sigmoid, and pulmonary semilunar valves which guard the orifices of the aorta and pulmonary artery respectively. Both sounds are therefore valvular, and any rent, or inequality, or imper- fection in the valves, permitting the blood to flow in the wrong direction, or causing friction, as in heart disease, causes alteration in the characters of the sounds easily recognized by the practised ear. The frequency of the beats of the heart is increased by exercise, by food, and by mental emotions. They are more frequent in the morning than at night, in the young than in the old, and in the female as compared with the male. The Nerves of the Heart. — The heart continues to beat in an orderly and regular manner even when quite removed from the body, and in the process of development the speck which represents it in the young begins to beat rhythmically long before any nerves arc formed. These circumstances show that its action is to a large extent independent of the great centres of the nervous system, whilst on the other hand the readiness with which the heart responds to disturbing conditions of the general system, in regard alike to the frequency and the strength of its beats, clearly indicates that it is under the control of certain nerves which can be demonstrated by anatomical as well as by physiological evidence to have intimate relations with it. The nerves distributed to the heart are derived from the spinal coixl and medulla oblongata, as well as from THE MECHANISM OF THE CIRCULATION 441 tlie sympathetic nerve. They have been divided into the accelerating and the restraining or inhibitory nerves. The accelerating nerves leave the spinal cord at the fore part of the dorsal region, and pass to the first dorsal ganglion of the great sympathetic chain, and after a short course are distributed to the heart. Stimulation of these branches causes the heart to beat more frequently. The inhibitory or restraining nerves of the heart are derived from the medulla oblongata, and run in the vagus nerve. Their peculiarity is that, instead of causing contraction of the muscle to which they are distributed, they induce relaxation, so that when stimulated they stop the heart in diastole, that is, in a condition of relaxation; whilst when less strongly stimulated they cause it to beat more slowly. The efiect is not, however, persistent, for even if the vagal branches continue to be strongly stimu- lated, the heart after a time recommences to beat more quickly and more strongly than before. The administration of belladonna, or of its -active principle atropine, prevents the inhibitory eflfect from manifesting itself when the vagus is stimulated, and a similar action is exerted by curara and by nicotine. On the other hand, muscarin, a poison obtained from a mushroom {Amanita muscaria), seems to stimulate or intensify the inhibitory influence. The heart is in unceasing movement day and night. Yet it has, like other muscles, its period of rest; for expenditure of force is only taking place during contraction, which occupies about one-half of the whole cycle of its action. It differs, therefore, from the ordinary muscles that are under the control of the will only in the circumstance that, instead of long spells of greater or less activity occurring alternately with the complete rest of sleep, its periods of work and rest have only short, intermissions. The force it exerts is immense. If we estimate that the quantity of blood driven out of the left ventricle at each contraction is the low amount of 1 pint or pound, and that it is raised about 10 feet, which represents the blood pressure, the work done is 10 foot-pounds per beat. Taking the number of beats at 40 per minute, we have 400 lbs. raised 1 foot per minute, or 1 lb. raised 400 feet. If this be multiplied by the number of minutes in an hour, and of hours in the day, the surprising number of 576,000 fuut-puunds, or more than 257 foot-tons, raised in twenty-four hours is obtained, which represents the work done by the left ventricle. The work of the right ventricle is estimated at one-third of this amount. The duration of one complete circulation of all the blood is about 27 seconds. The Blood-vessels.— The first vessels into which tlie blood is driven by the beat of the heart are the arteries. These are tubes which conduct 442 HEALTH AND DISEASE it from the heart to all parts of the body. Of large size where they commence, the pulmonary artery from the right ventricle and the aorta from the left ventricle, they divide and subdivide almost always at an acute angle till they terminate in the capillaries. They possess three tunics or coats. The outer one, sometimes named the adventitia, is thin, strong, and resistant, and is composed of connective tissue, with some elastic fibres; in it run the small vessels and nerves which supply the walls of the vessels themselves. The middle coat differs according to whether a large or a small artery is under observation. In the larger ^^,__^ arteries it is chiefly composed of elastic //^^^^$K\ fibres, with a few unstriped muscular fibres ^ .Mr wl interspersed amongst them. In the smaller CL 'Mar VKuv ™|j w \y arteries the elastic tissue becomes progres- ^ fwSL //•*l sively less and less marked as they diminish c — i:?-,*-- ^^ -y'^'^'s "^ ^^^®' being replaced b}' the muscular ^i'~ - ~r,f - * •-, tissue, which at last forms almost the whole /s' »' • :'• - "; thickness of the middle coat, the fibres for d vty.^.^-. -- :-\^ the most part running in a circular direc- \:\ tion. The internal coat is composed of a \, '-• ', ». '■ W'' sheet of elastic tissue with large apertures y/ '• ;if A «'- ' i' \\\ in it. It is lined by a layer of flat, endo- • " , > " ,, /';)■ thelial cells, which are therefore in contact ' "" * *■ '•' , ^,j^i;^ tjjg current of blood traversing the ' t'/ vessels. The nerves of the arteries form ^ ---__^,— ^.jr^'i-^^^ net-works in the substance of the vessel Fig. 192. -Transverse Section through a Wall. The scvcral coats of the arteries sraaii Artery and Vein eudow them with Strength to enable them A, Artery. V, Vein, a, EndotheUal CeUs ^q x&'&\^\> the UrCSSUrC of the blood, and alsO with Nuclei. 6, Elastic Layer of Tunica _ -"^ mi i intima. c, Tunica Media, rf, Nuclei of its with elasticity and contractility. The clas- Muscular Fibres, e, Tunica Adventitia, show- . . • i j. 1 J •„ j.!, 1 „ i. • ing Connective-tissue Fibres and Corpuscles, ticity IS bcst marked lu thc large artcrics, the contractility in the smaller ones. Both properties fulfll very important purposes. With each beat of the heart a pint or more of blood is suddenly injected into each of the great arteries. The shock and jar that this would produce through the entire system is almost entirely abolished by the great elasticity of the walls of the pulmonary artery and aorta. These vessels yield, and, greatly widening, receive the new column of blood with facility. But on the instant of the hear-t ceasing to deliver the last drop of its contents, they immediately recoil. The first eflect of the recoil is to close the semilunar valves, the next to cause the blood to move onwards and distend the next part of the artery in front. This having expanded, though to a TllK MECHANISM OF 'rilK CIRCULATION 443 less degree (for part o( the hlood in the arteries is escaping into the capilhiries), now retracts on the blood within it, and as the arteries at each division present a larger area, and therefore a broader stream, whilst more and more blood is entering the great capillary sea, the inter- rupted current oljserved in the larger vessels, due to the intermittent action of the heart, is gradually converted in the smaller vessels into a uniform, steady, and continuous stream. Thus the pulse, which is very perceptible in the larger vessels, becomes imperceptible in the smaller ones. Subsidiary purposes for which the elasticity is useful are that it enables the limbs to be freely bent and stretched and otherwise moved without risk of rupture. It also enables the arteries to accommodate themselves to the considerable variations that occur in the absolute quantity of blood in the system. Lastly, the elasticity of the vessels reduces the chances of death by hemorrhage, partly by retracting the cut artery in its sheath, and partly by diminishing its calibre. The elas- ticity of the vessels is not a new or active force in effecting the circulation ; it is passive, and represents the stored-up energy of the heart, which, during contraction, is expended in dilating the large vessels, and is given out again by them during the period of quiescence or relaxation of the heart. The Pulse. — The pulse is the wave -like movement which traverses the arteries with each beat of the heart, and which is perceived when a vessel is slightly compressed with the fingers against an unyielding surface. The arteries, in health, are always distended with blood, as shown by the spurt which takes place when one is divided, and when a fresh quantity is injected into it by the heart. The Contractility of the Arteries, unlike the property of elasticity, is feebly marked in the larger trunks and their primary branches, whilst it becomes more conspicuous in the smaller vessels. It is the means by which the supply of blood to the several organs is regulated in accordance with their condition of activity or repose. To take an example amongst many that might be given, the stomach during fasting receives a supply of blood sufficient to minister to the nutrition of the tissues of which its walls are composed. The vessels in this condition are contracted, and the colour of the organ is a pale pink; but after a hearty meal, when the process of diges- tion is in course of active performance, when gastric juice is being poured forth and absorption is proceeding, a much larger supply of blood is needed. Under the influence of certain (dilatator) nerves, by means of which the muscular tissue of the wall of the vessels is caused to relax, their calibre enlarges, a freer current of blood passes through them, and the whole organ becomes congested and of a deep rose-red hue. When the digestive process 444 HEALTH AND DISEASE is completed, and the blood-supply is no longer required, the contractility of the vascular walls comes into play again under the influence of another set of nerves (constrictor), chietiy proceeding- from the sympathetic system. The vessels now contract, the mucous membrane becomes pallid, secretion and absorption cease, and the organ resumes its normal condition in the fasting state. A similar succession of events may be observed in every organ of the body that undergoes variations in functional activity, as in the In-ain during mental effort, and in the muscles during exercise. Blood Pressure. — That when the skin is cut the blood spurts out is a proof that it is subject to pressure within the vessels. The Eev. Stephen Hales, the rector of Faringdon in Hampshire, was the first, at the beginning of the eighteenth century, to estimate what the degree of that pressure is in the living animal, and the animal he selected was the horse. He caused a mare to be tied down on her back, opened the main artery of the thigh, inserted into it a brass pipe the bore of which was ^ inch in diameter, and to this, by means of another brass pipe, which was accurately adapted to it, he fixed a glass tube, of nearly the same diameter, which was 9 feet in length. On untying the ligature previously placed on the artery, he observed the blood to rise in the tube 8 feet 3 inches perpendicular above the level of the left ventricle of the heart. This experiment was an original and a highly instructive one. It has often been repeated, not only in the horse, but in many other animals. The result of many observations has been to show that the pressure of the blood in the vessels is equal to that of a column of mercury 150 to 200 millimetres, or from 6 to 8 inches in height. But Hales pushed his experiment a step farther. He proceeded to investigate the effects of loss of blood on the general blood pressure. He measured the blood as it ran out of the artery, and after each quart of blood had escaped he refixed the glass tube to the artery " to see how much the force of the blood was abated ". This he repeated to the eighth quart, and then, its force being much lowered, he applied the glass tube after each pijit had flowed out. He noted several remarkable circumstances. First, that as each quart of blood was removed the blood pressure sank consider- ably, but after the lapse of a minute, more or less, it again began to rise, and although it did not rise to its original level, yet it ultimately attained, on each occasion, a level higher than that to which it had previously fallen. This, there can be no reasonable doubt, was mainly due to the vessels accommodating themselves by virtue of their elasticity and their con- tractility to the reduced volume of their contents. Again, it was found that the decrease in the blood pressure was not strictly proportionable to the quantity of blood withdrawn; indeed, it sometimes rose above the level attained during the previous emission, whicli was probably due to variations THE .MECHANISM OF THE CIRCULATION 445 in the degree of eontraetiou and relaxation of tlie luusoles in the walls of the vessels, and in the strength of the contraction of the heart. The blood pressure immediately rose when the animal strained its muscles to get loose —an ert'ect that was due to the muscular contractions, especially those of the abdominal muscles, forcing much blood towards the heart. In this cele- brated experiment about a quart of blood was lost in making the several trials, and Hales estimated that about 17 quarts were lost in all before the animal died. Taking into account the blood that was obtained from the vessels after death, he considered that 44 lbs. was a low estimate of the total quantity of blood in the horse. The cause of the blood pressure is twofold. On the one hand the heart is always engaged in driving into the vessels, which are already distended, or more than full, an additional quantity of blood; and on the other the current of the blood experiences great resistance to its onward passage in the smaller vessels, owing to their reduced diameter and the great friction that it consequently experiences in traversing them. The blood pressure would be much greater than it is were it not that, owning to the large number of the capillary vessels, the channel is greatly increased, the united area of the capillaries having been estimated to be eight hundred times greater than that of the aorta. The rate of movement of the blood through the arteries is estimated to be about 1 foot 8 inches per second. Prevention of Death by Hemorrhage.— Several circumstances concur to prevent the loss of life that would certainly occur, owing to the fluidity of the blood, when even a small vessel is divided. The first and most important of these is the almost complete closure of the opening of the tube by the contraction of the muscular tissue forming its walls. This tissue, as has been already stated, is most abundant in the small vessels which are chiefly exposed to such injuries. The closure of the vessel is of course aided by the elastic coat, which, being less and less distended, recoils as the blood pressure falls with the escape of blood from the system. Then the arteries are enclosed by a loose sheath, and when cut their proper walls retract to a considerable distance within it, leaving a narrow and tortuous passage, which impedes the exit of the blood. Again, the innermost coat of the artery is highly elastic, and has a tendency, when divided, to roll up within the artery, and thus to form a kind of valve, which is an additional obstacle to the escape of the blood. The coagulation of the blood of course plays an important part in arresting hemorrhage; a clot sjieedily forms in the loose tissue near the arterial or venous wound, which gradually stops up the opening and forms a plug for some distance up the vessel. Moreover, when much l>lood has been lost 446 HEALTH AND DISEASE the heart beats more rapidly, indeed, but much more feebly; and with faiiit- iiess and loss of consciousness the current of blood almost ceases. Finally, the convulsions that are the precursors of death drive the few remaining drops to the heart, and, by stimulating it to contract, afford the last chance of life being preserved. The Capillaries. — As the arteries proceed to the proper tissues of the body, they divide and subdivide till they are no longer visible to the un- assisted eye, and they finally break up into minute vessels named capillaries, the size of which is toleraljly uniform for each organ. These communicate freely with each other and form a mesh or web, the arrangement of which presents variations corresponding to the structure of the organ in which they exist, being ladder-like in muscle, tuft-like in the kidney, and basket- like round the lobules of fat and of glands. The wall of the capillaries is formed of a delicate basement membrane with a lining of flattened cells (endothelium), or even of the cells alone. Through this thin wall the white corpuscles of the blood seem to be able to bore without leaving any rent behind them, just as a needle may be thrust through the wall of a soap-bubble and withdrawn without causing the bubble to burst. The corpuscles then become free, and can move about in the interspaces of the adjoining tissues; but whether they die there or re- enter the vessels is unknown. This process, in which the white corpuscles pass out of the vessels, is named diapedesis. The current of blood is not always the same in the same capillary vessel, the direction being dependent upon the increase of pressure behind, that is, on the arterial side, or the relief of pressure in front or on the venous side. In examining the circula- tion in the capUlaries it will be seen that they are not large enough in many parts to admit two coloured corpuscles abreast, and they consequently follow each other in single file; but in the somewhat larger vessels the red corpuscles occupy the centre of the stream, whilst the white corpuscles roll lazily along at the margin in close contact with the inner surface of the wall of the vessel. It is in the play of the fluids within and without the capillary vessels that an important part of the processes of nutrition is transacted, the blood surrendering to the fluid which moistens their external wall the soluble materials for the nutrition of the tissues, whilst it takes up from that fluid the soluble products of the degeneration and decay of the tissues. The capillaries of the lungs are very large, and form a close net-work. Those of the brain are minute and less close. The average diameter of the capillaries may be taken to be a little larger than the diameter of the corpuscles of the blood of the same animal. The pressure of the blood in the capillaries is considerable, being capable of supporting a column of mercury about 1 inch in height. The rili; MlXllAMSM OF THE CIKCULATIUN 447 bloixl Hows tlirouuh tlie'in at the rate of about one twenty-fifth of an inc-li in a second. The veins; have thinner walls than the arteries, are more nunicious than they, and have much greater capacity, containing, according to the estimate of Haller, about twice as much blood. They communicate with each other bv large branches very frequently in their passage to the heart, and in structure very much resemble the arteries. The principal instance where veins do not convey the blood directly to the heart is the great portal vein, which conducts the blood from the intestines to the liver, and there breaks up into a second system of capillaries, which unite together again to form the hepatic vein; a similar arrangement occurs in the case of the kidney. In the veins of the neck and limbs, however, difterences are found in the form of numerous valves, usually arranged in pairs, and at tolerably regular distances from each other. These valves are composed of a reflexion of the inner coat, strengthened with some connective-tissue fibres, and near their base have also a small amount of involuntary muscle. The function discharged by the veins is to convey the blood back to the heart. The veins collectively, though there are a few exceptions, convey the blood to the heart, and run side by side with the arteries after which they are named. The radial artery is thus accompanied by the radial vein or veins, the brachial artery by the brachial veins. There are often two or more veins to one artery. The veins are more exposed than the arteries, as is seen in those of the neck, face, body, and limbs. Their capacitv is greater than that of the arteries, and the blood flows through them with a unifoim and continuous current, but more slowly, the velocity of the current being about 1 foot per second. They communicate freely with one another, and hence obstruction in any one vein is of less importance than in the case of an artery, since the flow of blood hindered or arrested in one channel of the former easilv finds escape Vjy another. The Chief Arteries and Veins. — We may now, with advantage, take a short survey of the chief vessels that have their origin in the heart, and which are engaged in the distribution of the blood through the system. The large arteries rarely join each other as do the veins, and the blood which traverses them always pursues the same direction. The capillaries, on the other hand, freely anastomose or unite together, and the blood they contain sometimes runs in one, sometimes in the opposite direction, through them; and as many arteries open into the same capillary net-work, this arrangement effectively prevents the serious consequences that would result in the case of obstruction or division of an arteiy, unless, indeed, the artery injured is a very large one, and is the parent trunk of the several arteries which open into the same capillary plexus. If, for 448 HEALTH AND DISEASE example, the aorta in a rablnt i.s tied aljo\e its division into tlie two iliacs, thus depriving the lower limbs of their whole supply of blood, the legs soon begin to drag, and become permanently paralysed, though even then, if the limbs are kept warm and preserved from injury, by placing the animal on cotton-wool, a secondary circulation through collateral vessels above and below the point of ligature may in course of time become estab- lished, and the power and action of the limb be restored. The pulmonary artery is a great trunk which arises from the upper and left side of the right ventricle. Its orifice is guarded by three semilunar valves (fig. 191, d), which are forced open at each conti'action of the heart, but close during its relaxation, and then completely prevent the return of the blood into the right ventricle. It conducts the blood to the lungs, and after a short course divides beneath the trachea into a right and left branch, which accompany the respective bronchi to the lungs, where they break up into many branches, and terminate in the capillary net-work that surrounds the alveoli or air-cells. The jiulmonary artery conveys impure or venous blood to be aerated at the lungs from whence it is returned, charged with oxygen and freed from carbon dioxide, by the pulmonary veins to the left auricle. Just before the pulmonary artery divides, an oblique cord (fig. 187, da) runs from it to the posterior aorta. This is an obliterated blood-vessel named the " ductus arteriosus Botalli ", which before birth transmitted the impure venous blood mainlv returning from the head and fore extremities to the trunk and hind-limbs. Immediately after birth, and as a result of the change in the circulation and the entrance of air into the lungs, this vessel ceases to convey blood and undergoes atrophy, becoming an impervious band. DISTRIBUTION OF THE SYSTEMIC ARTERIES Excepting as regards the lungs, all the arteries distributed over the system have their origin in the aorta (fig. 193). This vessel, the largest in the body, arises from the base of the heart, where it is continuous with the left ventricle, from which it is separated by the semilunar valves. It receives the blood discharged from that cavity at each contraction. The Aorta is a very capacious but short vessel, measuring onl}' from 2 to 3 inches in length. After leaving the ventricle it soon divides into two unequal parts — the anterior and the posterior aortas; but before doing .'■o it gives off two vessels, whose branches enter the substance of the heart for the nourishment of its tissue. These are the right and left corollary wteriefi:. Anterior Aorta. — This vessel, the smaller of the divisions of the A. First part of colon. B. Suprasternal flexure, c. Second part of colon. D. Pelvic fle.iure. E. Third part cf colon. F. Diaphragmatic flexure. 0. Fourth part of colon. H. Caecum. 1. Ilium. J. Great mesentery. K. Small intestine. L. Duodenum. Arteries of Stom.a,ch, 1. Left lobe of liver. 2. Middle lobe of liver. 3. Right lobe of liver. 4. Vena porta. 5. Hepatic artery. 6. Right sac of stomach. 7. Left sac of stoniacli. 8. Gastric splenic omentum. 9. Anterior gastric artery. 10. Posterior gastric artery. 11. Gastric artery. 12. Right gastro-omental arterv. 13. Left gastro-omental artery 14. .Spleen. l-"i. Splenic artery. Hi. Pyloric arterv. 17. Duodenal artery. DisTKii'.i 'I'loN i»K .\i;'i'i;[;iE.s-l Antkkiok Mksknteric Artery 1. Posterior aorta. 2. Anterior cum. .'). Superior ca?cal artery. 6. Ilio^csecal artery. 7. Bunch of arteries to stnall intestine 6. First artery to single colon, 9. Right colic artery. 10. Left or relrograrle colic artery. Spleen, Liver, Kidneys, &c. 18. Duodenum. 19. Right kidney. 20. Suprarenal capsule. 21. Right lenal artery. 22. Ureter. 23. Left kidney. 24. Left renal artery. .25. Left suprarenal capsule. 26. Left ureter. 27. Anterior mesenteric artery. 28. C'celiac axis. 29. Posterior aorta. 30. .30. Circumflex iliac arteries. :!l,3i. P^xtcnial iliac arteries. 32, 32. Internal iliac arteries. 33. Posterior vena cava. ^w ^ I I -^ X vO DISTRIBUTION OF THE SYSTEMIC ARTERIES 449 common aorta, i.s a))out 2 to 2| inches in length. Un leaving its parent trunk it passes in a forward direction beneath the trachea or windpipe, and soon divides into two unequal branches, one passing to the right and the other to the left. The right one is the arteria innominata, and the left one the axillary artery. The right branch is much the larger of the two, for in addition to giving blood to the fore -limb and the anterior part of the trunk, like its fellow, it also supplies the head by means of a large branch, the cephalic artery. Each of these vessels, on leaving the anterior aorta, gives off eight branches of considerable size, as follows : — 1. Dorsal. 2. Superior Cervical. 3. Vertebral. 4. Internal Thoracic. 5. External Thoracic. 6. Inferior Cervical. 7. Supra-scapular. 8. Subscapular. These vessels divide and sul)divide in their course, and furnish l)lood to the withers, the neck, the shoulders, and the walls of the chest. The vertebral artery requires special notice, inasmuch as it courses along the neck, partlv enclosed in small ])ony canals in the transverse processes of the six anterior cervical vertebrje. In its course it supplies many branches to the deep cervical muscles, and others which enter the spinal canal and are distributed to the spinal cord. After giving off the arteries above-named, the axillary descends along the inner aspect of the upper arm, where it takes the name of the brachial or hvnieral (irtery. Brachial or Humeral Artery. — This vessel descends on the inner aspect of the humerus and distributes branches to the muscles of the upper arm and other adjacent structures, the larger and more imjicrtant of which are — 1. Prehumeral, or Anterior Circumflex. I 3. Ulnar. 2. Deep Humeral, or Humeralis Profunda. | 4. Artery of the Biceps. On nearing the upper extremity of the radius or forearm the humeral artery divides into two unequal branches, the anterior and posterior radiuls . one, the smaller anterior radial, passes in a forward direction, and after distributing several small vessels to the extensor muscles, courses its way down the front of the leg as far as the knee, to which it furnishes numerous small branches. The Posterior Radial, much more voluminous than the anterior, descends on the inner side of the radius or forearm, where it is covered by the flexor metacarpi internus muscle. In its course along the limb the 2iosterior radial gives off branches to the elbow-joint, the flexor and extensor mu.scles, the skin, and also to the knee-joint. On reaching 450 HEALTH AND DISEASE the latter it divides into two: (1.) The small Metacarpal Artery. (2.) The large Metacarpal Artery. The former, superficially placed at first on the inner side of the knee, dips down behind the head of the canon-bone. It crosses to the outer side by pass- ing between the suspensory and the subcarpal ligament. Here it anasto- moses with a branch from the supra- carpal arch to form the subcarpal arch, which then proceeds to give oft" the anterior and posterior interosseous arteries, which supply blood to the structures behind and in front of the canon -bone, to the bone itself, to its periosteum or covering, and to the flexor tendons. The large metacarpal artery de- scends on the inner side and some- what in front of the flexor tendons until it reaches the sesamoid bones, where it divides into two parts, the internal and external digital arteries. These vessels pursue a downward course over the fetlock -joint, giving off branches before and behind to the tissues in the region of the pas- tern, and finally, entering the foot, they break up into a number of vessels and supply the frog, the coro- nary cushion, the sensitive laminae, the coftin-bone, and other parts con- tained within the hoof. This artery is situated between the plantar nerve behind and the internal metacarpal vein in front. Cephalic Artery. — This vessel, as we have jjreviously pointed out, is a branch of the right axillary and runs forwai'd beneath the tracliea until it reaches the entrance to the chest, where it divides into a right and left carotid arterv. Fig. 193. — DinKi-am of ('irciilation A, A, Posterior Vena Cava. B, Anterior Vena Cava. C, Pulmonary Artery. D, Hepatic Veins. K, Vena Porta. F, Renal Vein. 0, Spermatic Vein, H, Posterior Mesenteric Vein. > Pulmonary Vein ^ Anterior Aorta. ^, * Posterior Aorta. ° Splenic Artery. ' Hepatic Artery. '' Gastric Artery * Anterior Mesenteric Artery. ' Renal Artery ^" Spermatic Artery. " Posterior Mesenteric Artery. L.K., Left Kidney. n.K., Right Kidney, dia., Di.i- phragm. R.L., Right Lung. L.L., Left Lung. R.V., Right Ventricle. L.V., Left Ventricle, STOM., Stomach. SI'., Spleen. DISTRIBUTION OF THK SVSTKMIG MITi:i;iKS 451 Carotid Arteries. — These vessels iiscoml the neck, one on tlie ri^ht and tlie other on the left side of the trachea, in company with two important nerves, the vago-sympathetic and the recurrent. On reaching the larynx, they each divide into three vessels — the external carotid, the internal caiotid, and the dccipital. 1. The External Carotid supplies on each side the external parts of the head. It runs beneath the parotid gland, behind the angle of tlic jaw, and distributes its branches to the muscles of mastication, the submaxillary and sublingual salivary glands, the tongue, the palate, the pharynx, the lips, the ear, the teeth of the upper and lower jaw, and parts of the eye and membranes of the brain. 2. The Internal Carotid ascends on the outer side of the guttural pouch and enters an opening (Foramen laceruni) at the base of the skull; while on the floor of the cranium it unites by a cross branch with its fellow on the opposite side, and forms with it an arterial circle (Circle of Willis). It sends branches upward into the substance of the brain at different points, and thus ministers to its nourishment. The chief vessels of the brain are: The Anterior Cerebral. Middle Cerebral. Anterior Communica- ting. Posterior Cerebral. Posterior Communicating. Anterior Cerebellar. Po.sterior Cerebellar. 3. Occipital Artery. — This artery, given off by the carotid, is the third division. It passes up to the atlas or first bone of the neck, and after giving off the retrograde, mastoid and occipito-muscular branches to the small muscles of the poll, enters the spinal canal by an opening in the fu'st vertebra, and divides into the cerebro-spinal and occipito-muscular branches. The former on entering the spinal canal divides into two branches, one passing backwards along the spinal cord, and the other, going into the cranium, joins with its fellow on the opposite side to form the basilar. Posterior Aorta.- — This is a large vessel of considerable length situated immediately beneath the spine, along which it runs from the seventh or eighth dorsal vertebra as far back as the sacrum. It is the largest division of the common aorta, and in the first part of its course describes an arch backward, termed the aortic arch. The anterior portion of the vessel is situated within the chest, and is hence distinguished as the thoracic aorta, while the posterior segment occupies the abdomen, and is known as the abdominal aorta. It is, however, one continuous vessel, and these different terms are only used to denote its anatomical relations. As it proceeds backwards it passes from the chest into the abdomen through the hiatus aorticus, an opening between the two pillars of the diaphragm. The posterior aorta in its course beneath the spine gives off a number 452 HEALTH AND DISEASE of branches, some of which aie distributed to the walls of the chest aud abdomen, while others go to the various organs they contain. The former set include: (l) 13 jDosterior intercostal vessels, which run downward between the ribs and give ofi' branches upward to the muscles of the back and to the spinal cord. The first intercostal artery is derived from the superior cervical artery; the second, third, aud fourth from the subcostal branch of the dorsal. (2) Tlie phrenic, a branch going to the diaphragm or midrifi". (3) Branches to the muscles of the loins.. The second group comprise: (1) The bronchial arteries to the air-tubes and oe-sophagus or gullet. (2) The caeliac axis, a short thick vessel, which, after leaving the under surface of the aorta, divides into three unequal branches ^^.^^ ^j^^ Splenic. (h) The Gastric. (c) The Hepatic The first goes to the spleen, the second to the .stomach, and the third to the liver. A little farther l^ack it gives off (3) the great mesenteric artery, a short vessel of considerable size, whose branches are distributed to the large and small intestines. The next to appear are (4) the renal arteries, two short thick vessels, which spring from the sides of the aorta and enter the substance of the kidney. Still farther back come (5) the spei^matic vessels. These arteries, two in number, are of considerable length, and take a peculiar winding course downward to reach the testicles. In the female the uterine and ovarian arteries spring from this point, and, as their names imply, supply the uterus and the ovaries. Then comes the small mesenteric, whose branches are distributed to the posterior part of the large bowel, which is not supplied by the large mesenteric. Finally, the posterior aorta divides into two pairs of vessels, one pair going to the right and the other to the left. These are distinguished as — 1. The Internal Iliac Arteries. 2. The External Iliac Arteries. The Internal Iliac Artery breaks up into several divisions, which convey blood to the organs within the pelvis — the bladder, rectum, prostate gland, as well as parts of the uterus and vagina in the female and the penis in the male. They are: (l) the two last lumbar arteries; (2) the internal pudic artery; (3) the lateral sacral artery; (4) the ilio-lumbar artery; (5) the gluteal artery; (6) the ilio - femoral artery; (7) the obturator arterv. The External Iliac Artery, on leaving the aorta, runs down the inner side of the pelvis in an ol)lique direction backwai'ds and outwards. On reaching the anterior border of the pubis it enters the thigh and takes the name of the femoral artery. In its course it gives off the circumflex iliac artery, which is distributed to the Hank and to the thigh. A .small i)isTi;iiu;'ri()N of arteries— ii Arteries (M' Male Pelvis 1. Retractor penis. 2. Suspensory ligament of rectum, 3. Sphincter ani. 4. Rectum. 5. Vesicula; seniinales. 6. Urinary bladder. 7. Ureters. 8. Prostate gland. 9. C'owper's gland. 10. Vesico-prostatic artery. 11. Erector penis. 12. Suspensory ligament of penis. 13. Penis. 14. Posterior dorsal artery of penis. 15. Anterior dorsal artery of penis. 16. Vas deferens. 17. Epididymis. 18. Testicle. I'J. Spermatic artery. 20. Subcutaneous abdominal artory. 21. External pudic artery. 22. Posterior abdoniinal artery. 23. Deep femoral artery. 24. Prepubic artery. 25. Obturator artery. 26. Umbilical aitery. 27. Posterior aorta. 28. Second last lumbar artery. 29. Internal iliac artery. 30. Last lumbar artery. 31. Lateral sacral artery. 32. Gluteal artery. 33. Ileo-femor.d artery. 34. Internal pudic artery. 35. Artery of the corpus cavernosum. 36. External iliac artery. Arteries of the Brain 1. Anterior cerebral artery. 2. Middle cerebral arteries. 3. Anterior communicating arteries. 4. Internal carotid arteries. 5. Posterior communicating arteries. 6. Posterior cerebral arteries. 7. Bifurcation of basilar artery. 8. Anterioi' cerebellar arteries. 9. Basilar artery. 10. Posterior cerebellar arteries. 11. Cerebral branches of cerebro-spinai artery. A. C'erebral hemispheres. B. Cerebellum. c. Olfactory bulb. D. Optic cciiumissure. K. Pituitary body. F. Corpus albicans. 0. Olfactory tract, n. Crura cerebri. 1. Pons varolii. J. Medulla oblongata. 28 29 30 31 32 33 34 7 6 5 Arteries of lire male pelvis Arteries of the brain DISTRIBUTION OF THE AKTERIES-II DISEASES OF THE HEAET 453 lirancli goes to the spermatic cord, which in the mare goes to the uterus, and the prepubic artery, a vessel which divides into the posterior al>donunal and the external pudic arteries. The Femoral Artery extends from the os pubis above to the lower part of the femur, where its name changes to the i^opliteal. In its course downward it gives off several considerable branches, which are distributed to the muscles of the thigh. The Popliteal Artery, a continuation of the femoral, lies behind the femoro-tibial articulation or stilie-joint, and in fi-out of the popliteal muscle. After distributing small branches to the structures around, it divides into two parts — the anterior and posterior tibial arteries. Anterior Tibial Artery. — This is the larger of the two, and, as its name implies, is situated in front of the tibia or second thigh, down which it passes beneath the flexor metatarsi muscle. On reaching the tibio-tarsal articulation or hock-joint it takes the name of the great metatarsal artery. In its course down the leg it gives off a number of branches to the tibio- femoral articulation and to the muscles in its course, especially those in front of the tibia. Pedal or Great Metatarsal Artery. — This vessel is a continuation of the anterior tibial. It commences in front of the hock-joint, and passes obliquely outwards beneath the peroneus and the short extensor of the foot, to reach the furrow formed by the large canon and the outer splint-bone, along which it runs until nearing the fetlock-joint, where it passes inwards between the suspensory ligament and the large metatarsal bone, and divides into two branches — the right and left digital arteries. These traverse the sides of the phalanges or pasterns, and are ultimately destined to the fo(jt. The Posterior Tibial Artery lies deeply situated behind the tibia, and besides furnishing branches to the deep muscles of the leg it also supplies the nutrient vessel of the bone, and furnishes branches to the hock-joint. Finally it divides into the two j^lantar arteries. DISEASES OF THE HEART GENERAL CONSIDERATION OF THE PATHOLOGY OF HEART-DISEASE It seems to be agreed among veterinary writers that diseases affecting the heart of the horse are either not so numerous as those which attack the heart of the human subject, or that they pass to a great extent unnoticed until an opportunity is afforded for a post-mortem examination. Going back to the work of Gibson, who wrote in 1751, it will be 454 HEALTH AND DISEASE observed that after a description iu detail of tlie structure and functions of the heart and large vessels, he dismisses the pathology of the organ iu a short paragraph. " I have seen ", he says, " the hearts of horses frequently opened; sometimes there happens, as in the human body, collections of matter within the pericardium. I have seen pollipusses in the great vessels, sometimes a mass of slippery fat, especially within the left ventricle of horses that have died suddenly, and sometimes the heart itself is preter- naturally large." Since the time of Mr. William Gibson, surgeon, knowledge has ad- vanced, but even at the present day the subject of disease of the heart and large vessels is dealt with by veterinary writers in a very cursory manner. In the last edition of Mayhew's work on the horse, edited by Mr. James Irvine Lupton, it is remarked that disease of the heart is characterized by various names in scientific books, as carditis, pericarditis, hydrops-pericardii, inflammation of the pericardium, &c. All such conditions, the writer observes, in the horse were discovered by examination instituted after death, when, unfortunately, all opportunity of observing symptoms had ceased. Veterinary science cannot distinguish one state from another while life exists. May hew goes on to state that " diseases of the heart in horses are incurable", and suggests that it is jaossibly on that account that "apparently little attention has been paid to the diagnosis and treatment of them". Remarking on the absence of characteristic symp- toms, he adds that auscultation affords the surest means of detection. Any unusual sound, he says, being audible, the examiner may conclude that the heart is diseased. In further description of symptoms it is stated that " the visible signs are sometimes sufficiently emphatic to admit of no doubt " ; the eye is expressive of constant anguish, the countenance is haggard, the pulse is feeble and irregular, and the heart-throbs are visible and frequent; they are to be seen as plainly on the right side as on the left. Regurgitation within the jugular veins is nearly always excessive, the blood often reaching almost to the jaw." The difference between the estimated importance of heart-disease in man and the lower animals is emphasized by Mayhew, and indeed is urged in explanation of the comparative indifference with which these diseases have been regarded by the veterinary surgeon. The veterinarian is seldom called upon to treat heart-disease, and has not the same experience of dis- eases affecting this organ as has the physician, for the reason that man, even when suffering from an incurable ailment, must be treated, but the horse in a similar state is usually sent to the knacker; consequently it is from human medicine that the most valuable information has been received. These remarks are strictly correct, and fairly estimate the circumstances DISEASES OF THE HEART 455 wlik'h have enabled the iiicinlieis of the veteniiaiy pmiessioii to leeuuiiize tlie eliiiit-al syiiiptoiii.s of .some of tlie diseases of tlie heart of tlie lower animals, which they can now diagnose with almost absolute certainty, although it still remains true that the physician has enormous opjjor- tunities and facilities in the examination of the heart of the human subject which are not, and cannot, under any possible conditions, be possessed by the veterinary surgeon. The heart of the horse and other large mam- malians is so perfectly covered by the bones and muscles of the upper part of the fore extremities that it is absolutely impossible to apply the stetho- scope or the ear over every portion of the organ, as can be easily done in the human subject; further, the instrument cannot be employed with the same advantage as it possesses in the hands of the physician. Even in those parts which can be reached, the covering of hair interposes an ob- struction w'hich considerably alters and obscures the sounds which can be recognized, and it is on this account that the majority of veterinary surgeons content themselves with the application of the ear to the part of the animal which they wish to auscultate instead of using the stethoscope for the purpose. In this connection, however, it may be observed that the ear is a very poor substitute for the stethoscope when the latter is in a practised hand aided by an educated ear. Of the fact that the heart in the lower animals is subject to most of the diseases which are well known in the human subject, the experience which has been gained by post-mortem examination has afforded abundant evi- dence, and the veterinary pathologist has no difficulty whatever in recog- nizing the true characteristics of the various morbid conditions which are exhibited after death. His difficulty is confined entirely to the detection of each .special form of disease in the living animal, and while he would not be content to accept Mayhew's imputation, that veterinary science cannot detect one state from another while the animal is alive, he would without hesitation admit the great difficulty of arriving at a satisfactory conclusion from symptoms which may be present at the time of his examination. Certainly it is the case that some of the most marked symptoms which Mayhew describes would not necessarily suggest to him the existence of any disease of the heart. In connection with the subject of clinical symptoms it is fully recog- nized by the physician that the evidences of disease, or evidences which may be construed into signs of disease, of the heart, may be present in parts of the system remote from the organ itself. There is nothing at all remarkable in this proposition when it is remembered that the heart is the organ which distributes the blood over the whole of the body, and is there- fore connected more or less directly with every other part of the system. 456 HEALTH AND DISEASE The uatural result of this is, that diseases of remote structures or distaut organs may so adversely inilueuce the heart as to lead to indications which may easily, although incorrectly, be ascribed to derangement of the central organ itself; on the other hand, disease of the heart expressing itself by detectable alterations in its own sounds and movements is responsible for various forms of disturbance which occur in the digestive organs, liver, kidneys, or lungs, or some other parts. At the same time, it is thoroughly well recognized, as a fact about which there is no question, that grave structural and functional disturbance may affect the heart without leading to any manifestation at all which can be recognized as relating to that organ. In other words, an animal may die suddenly from heart-disease the existence of which had never been suspected during its life. Among the .symptoms which are frequently referred to disease of the heart are those which are described as subjective — that is to say, sensations which originate in the consciousness of the individual, such as pain, either continual or spasmodic, oppi'ession in the chest, momentary stoppage or disturljauce in the movements of the heart, dizziness, paljjitations, and sinking. That these sensations, which are realized by the patient, are usually attended with extreme distress and apprehension will be readily understood, although it is a fact that all these clinical signs common in heart-disease may be experienced without any disease of the heart itself l)eing present. From the risk of error due to the existence of subjective symptoms, which would be usually classed under the head of extreme nervousness on the part of the subject, the veterinary surgeon is aljsolutely free. His patients either have no nervous apprehensions in regard to the state of their hearts or other organs, or, if they have, do not possess the means of expressing them in an intelligible manner. Admitting, as must be the case, that disease of the heart of the horse is not so uncommon as it has been considered to be, the important question arises as to the best method of examination, for the purpose of detecting any obscure symptoms, which may be sufficient to direct the attention to the condition of the heart and the vessels immediately proceeding from it. At the commencement it must be distinctly understood that while the veterinary surgeon is not subject to the risk of making an incorrect diagnosis in consequence of subjective symptoms or sensations which the horse cannot declare, he has to incur an equally prominent risk of arriving at a wrong conclusion in consequence of the derangement of the heart leading to disturbance of some other organs. The respiratory organs are, of course, most likely to be acted on. Any serious derangement of the central organ of circulation must necessari]\- intei-fere with the cir- DISKASKS OF Till-: IIKAKT 457 (.■ulatioii of lilood tlu-ou^h [\\c luii^s; aii\tliiii,<;' wliicli leads to excessive contraction of the rioht ventricle, by which the l)lood is forced into the kings directly, or any interference with the action of the left side of the heart arising from deficient contractile power or mechanical obstruction in the passage of blood through the left auricle or ventricle, would natui'ally induce a state of engorgement of the vessels, or congestion of the lungs, which would be indicated by symptoms which the veterinarian recognizes without difficulty. The breathing would become rapid and oppressed, the surface of the body would very quickly become cold, and from other signs the examiner would very quickly diagnose congestion of the lungs. The affection may be sufficiently severe to justify him in calling it pulmonary apoplexy. Such a diagnosis would be in effect strictly correct, although it may leave out of consideration altogether the real cause, viz. : the blocking u}) of the vessels of the lungs with stagnant blood, not on account of any derangement of the respiratory organs themselves, but entirely owing to the circumstance that the heart is in such a condition that it is incapable of carrying on the pulmonary circulation. It does not follow that the congestion of the lungs arising from .defec- tive action of the heart should take place suddenly to such an extent as would lead to any serious disturbance in the breathing, or justify the diagnosis of pulmonary apoplexy. Any mechanical difficulty affecting the circulation of blood in the lungs, whether arising from some impaired action of the heart or from any other interference, would lead to attacks of difficult breathing, cough, sometimes rupture of small vessels followed by bleeding from the nostrils, noises in respiration when it becomes at all hurried, sudden attacks of spasm, and in some cases a condition of the breathing which may lead to the impression that the horse is suffering from broken wind. Attacks of indigestion, and even gradually increasing emaciation, representing that state of the system which is expressed by the horseman's term " bad condition ", are all indications which may be really consequent upon functional or structural derangement of the heart, al- though there may be no symptoms which specially direct attention to it. As disease advances, more sti'iking symptoms become evident. The wasting may be associated with dropsical effusions in the lower extremities and also along the inferior part of the aljdomen, and there may be also more serious forms of dropsical effusion into the heart-sac (pericardium), the cavities of the chest, and abdomen. Chronic derangement in the central organ of circulation also leads to nervous derangement, in which the brain is commonly implicated. In the human .subject, under these circumstances, the symptoms are easily recognized. The patient complains of frequent or even constant headache, with a feeling of fulness and heat 458 HEALTH AND DISEASE about tlie head, rushing noises, throljbings. Hushing of the face, giddiness, sleepiness, irritability, impairment of the intellectual powers, or actual mental derangement, disturbance of vision, movement of bodies before the eyes, twitchings in the extremities, and attacks of faintness. It will be perceived that the majority of these symptoms would not be recognized in the lower animals, and the few that would be apparent, such as unsteadiness of movement, attacks of vertigo (megrims), or twitching in the extremities, would possibly not be attributed to disease of the heart, and would probably not be in any way connected with disturbance of that organ. Under such conditions it is evident that a diagnosis must neces- sarily be of an uncertain character, unless by some accident suspicion of the true cause be aroused, and a careful examination of the heart lead to the detection of certain morbid conditions. Physical Examination of the Heart and its larger vessels can only be undertaken by an expert who is familiar with the anatomy and physi- ology of the organs of the circulatory system, and on this part of tlie su})ject the reader is advised to consult the sections on the anatomy and j)hysiology of the heart. Armed with the knowledge thus obtained, even the tyro will be able to realize the importance of constant experience in the use of the instruments which are employed for the purpose of the exami- nation of the heart and vessels, even if he does not contemplate devoting himself sufficiently to the subject to obtain the necessary skill. In the first place, the examination which will be required will have regard to what can be ascertained by the use of the hand applied to the cardiac region, and also to certain of the most superficial arteries. The amount of force exercised by the heart in its contraction produces a distinct impres- sion to the hand of the examiner when placed upon that part of the walls of the chest against which it strikes or beats, and the impulse communi- cated by the heart to the blood which passes through the arteries produces a beat as nearly as possible at the same time as the contraction of the heart. This is described as the pulse, and upon its character and frequency some opinion may be formed as to the general condition of the central circulatory organ, as previously described in the section relating to the symptoms of disease. In the next place, percussion over the cardiac region, performed by a light but sharp stroke with the points of the fingers, will make the examiner acquainted with any alteration in sound as compared with that emitted from the chest of the perfectly healthy subject. For example, where dulness of sound is found to extend beyond the area of the healthy heart, enlargement or hypertrophy of the organ would be suspected. Next to percussion, auscultation is emplo}'ed l)y the use of the stetho- DISEASES OF THK HEART 459 scope ill Iiuiiiaii pructii'L', liy the application of the ear to the part wlieic the lower aiiinuiLs are concerned. Tlie object of this form of examination is to distinguish any almormal sounds which may exist in connection with the beats of the heart. These sounds can only be distinguished by the expert who is familiar with the healthy sounds, which may be described as far as it is possible to describe them in words as follows: — First, there is a sound which is believed to be produced by contraction of the ventricles. This is called the i<;ystolic sound, and it is also distinguished as a long sound, the term being used, of course, comparatively. This systolic sound is followed by a short interval of silence, which is succeeded b}^ the second, descriljcd as the diastolic sound, which occurs when the ventricles cease to contract, and the valves guarding the pulmonary vessels and the aorta close. The diastolic sound is followed by a rather longer silence than that which succeeds the fu-st, and then the systolic or first sound recurs. The duration of the sounds and intervals is expressed by dividing the whole period occupied by the series into ten parts, and then subdividing as follows: — Systolic sound -^, first interval -j^, diastolic sound -^g, and second interval -^. The actual character of the sounds as they strike the ear has been expressed by Dr. C. J. B. Williams by the words "lub-dup". Very little difliculty would be experienced in rendering the ear accustomed to the normal sounds of the heart, but it must be clear that an accjuaintance with the abnormal sounds and their meaning could only be acquired by long practice with the assistance of a comj^etent instructor. The most that the tyro could hope to achieve in this direction without such assistance would be the recognition of a change from the normal sound of the heart or its large vessels, and he would arrive at the knowledge simply from the observation that the normal sound with which he had rendered himself familiar had undergone certain modifications. The expert, in making an examination, not only realizes the fact that there is a change from the normal sounds to the abnormal, but he dis- tinguishes also the seat and cause of the abnormal murmurs; for example, variations as to the intensity of sounds, whether increased or diminished, alteration with regard to pitch and clearness of the systolic sounds, will inform him as to the condition of the valves and walls of the heart. A very clear, sharp, high-pitched, systolic sound will be more commonly heard in cases of anaemia, or extreme debility; again, alterations in the duration of the sound give important information as to the condition of the heart. In dilatation of the ventricles, with increase in the thickness of the walls, the systolic sounds will be prolonged, and the diastolic sound will probably be much shortened and very much obscured; whereas, in dilata- 460 HEALTH AND DISEASE tion of the cavity, without auy alteration in the thickness of the walls, the diastolic sound is longer than normal, while the systolic is shortened. The pathologist also obtains a great deal of information while examin- ing his patient by comparing the sounds which are heard in different parts of the chest, especially over those parts which correspond to the lower part or apex and the upper part or base of the heart. If the sounds are weak at the apex and louder at the base, the evidence is accepted as serving to distinguish effusion into the heart-sac (pericardium) from dilatation of the cavities or fatty condition of the heart. Intense sound at the right apex over and above that at the left may indicate either displacement or enlargement of the right side of the heart ; it also occurs when a portion of lung unduly distended with air (emphysematous) is interposed between the heart and the walls of the chest. A murmur or, as it is commonly called, "bruit" is generally taken to indicate friction at some point over which the blood is passing, and in the majority of cases it is allowed that the murmur depends on some morbid condition of the valves which guard the orifices of the heart. There are certain situations in which the murmurs relating to different parts of the heart are most readily heard. Thus murmurs connected with the mitral valves (fig. 191) are described as loudest just above the apex beat, while the murmurs which are connected with the valves of the aorta are most marked at the base of the heart. In the descriptions which are given in works on pathology a much more intricate and extended account of the different sounds in different positions is given, but sufficient has been written to indicate to the reader the very abstract character of the subject, and the enormous difficulties which attend a critical examination of the heart with a view of making a correct diagnosis of any existing disease. Indeed, with all the facilities which the physician possesses, including the use of the most elaborate and perfect instruments, the power to place his patient in any position which he thinks most convenient, and of regulating the character of the respirations with regard to their depth and frequency, or of arresting the action altogether for a short period, so as to obtain absolute silence in the respiratory organs of the chest, there is still a considerable difference of opinion existing among experts as to the cause and meaning of certain sounds which can be recognized. Diseases of the heart and its connections are for convenience divided into those which aflect the membranes enclosing and lining the organ, and those attacking the muscular structure of which it is chiefly compased. Thus we have acute or chronic inflammation of the membranous sac in the double layer of which the heart is comijlctely invested, and similar afiec- DISEASES OF THE HEART 401 tions involving the tino nionihiane' which lines tlio cavities of the heart, and these two niorliid states are designated l)y different terms according with the position occupied by the structures. Where iuHaniuiatiou iiH'ects the former it is spoken of as pericarditis, or inflammation of the investing membrane; while the term endocarditis is used to indicate inflammation of the membrane which lines the cavities of the heart and contributes to the formation of the ditierent valves. Inflammation of the valvular structures is also distinguished by the term valvulitis. Inflammation, acute or chronic, of the muscular structure of the heart is described as myocarditis, which is commonly associated with inflammation of the membrane investing or lining the heart. PERICARDITIS— INFLAMMATION OF THE HEART SAC Inflammatiou of the pericaulium may occur under a variety of circum- stances, sometimes in connection with rheumatism, strangles, and influenza, or auv low form of fever or specific blood disease. It may also arise from injury, such as a wound inflicted from without, or from the passage of some foreign body from the digestive organs, through the diaphragm into the pericardial sac. This cause is comparatively frequent in cattle, but is extremely rare in the horse. One case is recorded in which a sewing- needle had passed through the oesophagus into the pericardium, and subse- quently reached the right auricle of the heart. As in other cases of disease connected with the central circulatory organ, pericarditis, especially the chronic form, may exist for a considerable period without any symptoms being present which would lead to the suspicion of its existence. This is particularly the case in reference to what is called traumatic pericarditis in cattle. These animals, when at pasture, frequently swallow various extraneous substances which come in their way, and among foreign cattle kept by small owners, and fed very much about the dwelling- houses, it used to be extremely common to find in the rumen of the animals, which were sent to this country for slaughter, various domestic articles, such as brushes, tin or other toys, hair-pins, shawl-pins, skewers, knitting- needles, and even portions of wearing apparel. In post-mortem examination it frequently happens that a needle, or piece of wire, or a skewer, is detected in the heart sac, and its path can be traced through the second stomach [reticulum), which lies close to the diaphragm, and from that organ into the pericardial sac, and sometimes into the muscular structure of the heart. In other cases, where the body which has inflicted the injury has been lost in the course of the examina- tion, the path which it has taken can be distinctly followed from the 462 HEALTH AND DISEASE second stomach into the heart sac. This condition of things has not un- commonly been observed in animals in good condition sent to the slaughter- house without any suspicion arising that they were subjects of such severe injuries. Symptoms. — The symptoms of pericarditis of the acute form are very often complicated with those of ordinary inHammation of the lungs and pleura (pleuro-pneumonia), and indeed, in fatal cases of the latter disease, it is quite usual to find indications of inflamed pericardium. In such cases as the above there would, of course, be great difficulty in separating the symptoms belonging to each set of organs, but it is generally allowed that the character of the pulse, the irregularity of the heart's action, and the presence of a venous pulse in the jugular vein may be taken as indications that the heart sac is implicated in the inflammatory condition. In pericarditis resulting from injury it is certainly the case that the disease may advance to a considerable extent before any symptoms of illness are apparent; in some cases there may be no particular signs of derangement until the foreign body, needle or skewer, reaches the heart. It has been noticed at the termination of these cases, when the fact of the existence of the disease has been made patent by a post-mortem examina- tion, that the animals for some time before death have been subject to frequent attacks of indigestion, associated with elimination of gas into the rumen in the case of cattle, and into the single stomach of the horse. As a result of the disease, a quantity of fluid, clear or turbid, is usually found in its cavity, with adhesion of a portion of the membrane perhaps to the heart, and sometimes considerable thickening of the structures. Pericarditis which is independent of the passage of any foreign body or other injury is distinguished as idiopathic, a form which seldom occurs unless in combination with pleuro-pneumonia, and, as previously stated, it is scarcely likely that it would be distinguished at once as a distinct disease in the presence of inflammation of the lungs and pleural membrane. In the event, however, of any suspicion being excited which would lead to an examination of the heart by the application of the ear to the left side, over the cardiac region, it would be discovered that the normal sounds of the heart are less distinct, and if fibrinous exudation has taken place between the two layers of the pericardium, friction sounds might be detected in the eai'ly stages of the disease. Treatment of the idiopathic form of pericarditis may be attempted witli some hope of success. It would include the administration of a saline aperient, and in some instances, when the symptoms are very marked, and the heart is aftected witli palpitations, digitalis is recommended. Fomenta- tions, or the JKit ]iack, or counter irritation to tlie region of the heart, may DISEASES OF THK HEART 463 also lie eiiipluyeil. The liody should lie well clothed and the legs haiidaged, while the strictest quietude should he insisted on. ENDOCARDITIS— INFLAMMATION OF THE LINING MEMBRANE OF THE HEART This disease is said to be more frequent in the horse than the one which has just been referred to. When it occurs in association with rheumatism, it is more likely to end fatally in a short time than ordinary intlammation of the pericardial membrane, in consequence of the liability of the valves to undergo thickening, and the blood to coagulate upon them and u[)on the surfiices of the heart's cavities. Symptoms indicative of endocarditis of the ordinary kind have been difi'ercutly described by different observers. The physical signs of the disease are : excited action of the heart, and the presence of certain sounds which are described as endocardial murmurs. The friction or rubbing sound which is recognized in pericarditis will not usually be present. It is somewhat remarkable that little or no pain is manifested during the pi'ogress of the malady. The pulse at the commencement is frequent and full in its beat, afterwards becoming feeble and irregular. Fever is sometimes very pronounced, and at others it tends to assume a low subdued form. The results to be apprehended are deposits within and upon the valves and round about some of the orifices, thus interfering with the passage of the blood, and leading to obstruction and the formation of large fibrinous clots. These are not unfrequently broken up into small frag- ments by the movements of the heart, some of which are carried along the course of the circulation, and may thus lead to fatal obstruction by lilocking up vessels in important organs. The malignant forms of the disease, associated with the formation of abscesses and ulcerations, have only now and again been recognized in the horse. Treatment. — When the disease is complicated with an attack of rheumatism, salicylic acid and its salts must be resorted to and persevered with to check the progress of the disease. Perfect rest must be enforced and every form of excitement avoided. The bowels should be gently acted upon as required by the administration of small doses of sulphate of mag- nesia, and any manifestation of heart weakness must be met by the careful employment of digitalis and ammonia. 464 HEALTH AND DISEASE MYOCARDITIS, OR INFLAMMATION OF THE MUSCULAR STRUCTURE OF THE HEART This disease occurs very rarely in the lower animals, and most prol)alily when it does happen it is connected with other diseases which have been described, i.e. pericarditis and endocarditis, in both of which the iuHamma- tion may extend to the muscular structure. Continental writers refer to myocarditis as an infectious disease associ- ated with aphthous fever, septicaemia, tuberculosis, and contagious pneumonia of the horse. The alterations which are occasioned in the mu.scular structure will depend upon the activity of the inflammatory condition. Among them may be mentioned softening, and difierent degrees of degeneration, which weaken and impair the functions of the organ. In its chronic form the disease tends to the development of hypertrophv or enlargement, hardening of the muscular structure, and difierent forms of fatty and fibroid degeneration, and in some instances .small abscesses are formed in the muscular walls. Symptoms of myocarditis are not of a sufficiently definite character to lead to a correct diagnosis. In the majority of cases the j^ulse is weak, sometimes hardly detectable, generally increased in frequency, and the respii'ation is rapid and carried on with difficulty. Sometimes, when caused to turn, the animal grunts, and deep pressure over the region of the heart causes pain. There is also weakness, incapacity for work, a fastidious appetite, and occasional attacks of vertigo, especially in the advanced forms of the disea.se. There is an absence of the morbid sounds which are observed in cases of pericarditis and endocarditis, and in valvular disease. DISEASES OF THE VALVES OF THE HEART Endocarditis in the chronic form may be expected to lead to a certain alteration in the valves which guard the ojienings leading to and from the different cavities of the heart. The alterations of structure may consist of thickening of the valves, adhesion of one to the other at their edges in particular, and to the walls of the cavities. In some cases they develop large excrescences, or, as they are sometimes called, cauliflower growths, which occupy a considerable space in the cavities of the auricles or ventricles. (See Coloured Plate.) Among the domestic animals the pig appears to be most subject to these growths, which have been constantly found in the post-mortem examinations of animals which have died or been slaughtered in consequence of swine fever. I'l Mr \\\| A, A. \ahcs of the Heart much thickened as tlie result of Valvular Disease I B Calcareous de.^encration of the mitral valve A, A. Fibrous tissue B, B, B. Calcareous degeneration Fibrous vegetation of the mitral valv VALVULAR DISEASE OF THE HEART (Endocarditis) DISEASES OF THE HEART 4G5 Many years ago Youatt referred to the Lomiuon proHeiice of these vegetations in the heart of the pig, and he noticed in particiUar that tlie animals in which the disease was detected in the shiughter- houses had given no evidence whatever of the existence of such tumours during life. Valvular disease in the heart of the horse is, according to Professor Nocard, more common than it is suspected to be. He has given a table of the relative frequency of the different valvular affections in that animal. Of forty-two subjects it was found that thirty-eight had disease of the valves of the aorta. In the other four, disease both of the aortic and mitral valves was detected. In some cases one of the normal sounds is obliterated, or may be reduplicated, or it appears every other or every second beat. The character of the morljid alteration varied considera])ly. In some cases the valves were merely thickened and hardened, in others they were contracted, sometimes they were indented or perforated, and in others they were covered with fibrinous deposits. In the cases referred to, the diagnosis had been made during the life of the animal, and in almost all of them a blowing noise, which occurred during what would ordinarily be the interval between the normal sounds, was detected by auscultation. It is remarked by Dr. W. L. Zuill, in his translation of the work on pathology by Drs. Freidberger and Frohner, that the first symptoms of this chronic inHammation of the lining membrane of the heart is the marked weakness of the animals while at work. They will stop, refusing to advance, and do not respond to the voice or to the whip. Treatment is not likely to be attended with any great advantage. The recommendation to avoid excitement and any active exertion is tantamount to proposing to keep the affected horse in the condition of useless idleness. For the purpose of temporary alleviation of the most marked symptoms, the use of iodide of potassium with digitalis is recommended, but, excepting where some special value is placed on the patient, economy, and humanity too, would be best considered by having him destroyed. HYPERTROPHY— ENLARGEMENT OF THE HEART The different forms of disease and deformity affecting the valves, which have been adverted to in the preceding remarks, necessarily cause obstruc- tion to the circulation, attended with regurgitation of the blood and increase of pressure in some of the cavities of the heart. Any obstruction arising out of disease of the valves is likely to occasion enlargement of the heart in one or another part of the organ according to the particular valves affected. 466 HEALTH AND DISEASE Obstructive disease of the aortic valves gives rise to thickening of the walls of the left ventricle, while the same condition of the pulmonary valves would similarly affect the right. Enlargement of the heart may arise from increase in the development of the muscular structure (hypertrophy of the muscular w-alls), or from dilatation of the cavities from extra pressure from within. But it is pretty generally recognized that the same obstruction which gives rise to hyper- trophy will also occasion dilatation of the cavities, hence it is found that both conditions usually exist to a greater or less extent at the same time. The heart of the horse, which in a normal condition weighs about seven or eight pounds, may be increased in this disease to twelve or more pounds. Hypertrophy and dilatation are much more common in the left ventricle than in the right, for the reason that the valves of the former are more liable to sprain and disease than those of the latter. It will be remem- bered that the left ventricle sends the blood over the entire body, while the function of the right is confined to distributing it over the lungs. The work entailed in the former act being so much greater than that of the latter, the chances of obstruction to the blood flow are correspondingly increased. Thus the aorta, the vessels of the kidneys or the liver, or those of one or more of the various organs of the body, may by disease become narrowed, and tend to obstruct the circulation, which in time the heart would attempt to overcome, and its increased effort would have the effect which follows all muscular work, of sooner or later causing thickening of its walls. If the obstruction continued, or for any reason became worse, dilatation of the heart would follow hypertrophy. In these cases the valves which guard the orifice are required to stretch in order to fill up the still larger opening, or they sprain and become diseased. It does not necessarily follow that because the heart is enlarged its walls should be thickened. This will frequently depend upon the amount of dilatation which it has undergone. In some cases the walls are much thinner than normal owing to the hypertrophy not having kept pace with the dilatation. Symptoms of Enlarged Heart— It is certain that very considerable changes may take place in the muscular structure of the heart without any symptoms at all being apparent. When, howcvci-, the changes are such as to disturb materially the function of the organ, the disease is rendered apparent by very obvious signs, afforded in the first instance by a physical examination of the chest. If the enlargement be due to hypertrophy, the impact of the organ against the walls of the chest will not only be increased in intensity, but it will be felt over a much greater area than normal wlicii DISEASES OF THE HEART 467 the open hand is placed over the region of the lieart. Moreover, the area of the dull sounil commonly invoked by percussion is extended in proportion as the heart is enlarged, and this is tlie case whether the enlargement arises from hypertrophy or from dilatation, or both combined. There is, besides, more or less palpitation, especially under circumstances of exertion and excitement. The usual recommendations to avoid excitement and fatigue are given when the disease is diagnosed, but as a matter of course, unless it is in such a stage that the rest that would be necessary need only be temporary, the animal is rendered perfectly useless, and might as well be destroyed. In fact, this alternative appears to be the reasonable one in all cases in which the disease is indicated by marked symptoms. For example, when an animal affected with a large heart — whether it consists in simple hyper- trophy or only dilatation, or of the two conditions together — suffers from increased respiration when at rest, and to a greater extent during exertion, with the addition of staggering, attacks of vertigo, trembling, sometimes convulsions, and frequently derangement of the digestive organs, leading to loss of condition, emaciation, and ansemia, it may be concluded that the chances of recovery are .so remote that it is not worth while to attemjDt any treatment. ATROPHY OF THE HEART This condition, which refers to a diminution in the size of the organ owing to wasting of the muscular tissue and a general failure of its con- tractile power, is much less common than the enlarged state, hypertrophy and dilatation. The characteristic symptoms are those which would be expected from the anatomical changes. The circulation becomes extremeh' feeble, the pulse is small and weak, and general failure of the supply of blood to the whole of the system leads to passive congestions in different organs and rapid emaciation, which would terminate fatally if the end were not anticipated, as it usually would be, by .slaughtering the animal. FATTY DISEASE OF THE HEART Two perfectly distinct conditions are included in the term fatty disease of the heart. One consists in mere infiltration of the fatty material among the muscular fibres of the heart, which may be observed in animals when overfed (fatty infiltration), and the other con.sists in the actual conversion of the muscular structure into fat (fatty degeneration). In the former, the cells in the connective ti.ssue between the muscular fibres become filled with fat, and there is an excessive deposit of fatty material outside the 468 HEALTH AND DISEASE heart and round the base, and in the grooves in the walls of the organ, along which the blood-vessels pass. In connection with this dejxjsit of fat the muscular structure becomes pale and flabby. Symptoms. — Fatty infiltration is found to exist in the case of animals which spend an idle life or do very little work, and are supplied with an undue quantity of food. Such animals are usually referred to by stable- men as being in soft condition, and it is recognized in reference to them that they are incapalile of active work, rapidly becoming exhausted and sufl"ering from shortness of breath and palpitation of the heart on slight exertion. The circulation is necessarily weak and languid, the extremities are cold, and an examination of the heart would reveal the characteristic symptoms of feeble impulse and much- diminished intensity in the normal sounds; when the deposit of fat is ex- cessive, it may happen that -no sound can be detected at all. The condi- tion is modified by the circumstances under which the fatty infiltration takes place. In horses which have been fed to be brought into what is known as dealer's condition, a process which has probably only occupied a few weeks, regular exercise and change in the character of the food will, in the majority of cases, restore the animal to a healthy condition. It is only after the excessive feeding, with in- sufficient exertion, have been continued for a long period that the diseased state is likely to become permanent, and even in such cases considerable improvement in the animal's condition may be eft'ected by persistent employment of the ordinary measures, which would come under the head of physical training, including carefully-regulated exercise, the avoidance of food containing a large proportion of fattening material, and the careful adjustment of the food given to the quantity of work performed. Fatty Degeneration. — This condition of the heart may be associated with long-continued fatty infiltration, or it may follow an attack of inflam- mation (Myocarditis), or arise in the course of some wasting disease, or as a result of one or another of the acute specific fevers. It is mostly found to exist in old animals, and the progress of the malady is consider- ably favoured by a sedentary life; in fact it may occur in an exaggerated form in animals which are not ]ilethoric, although it appears that want Fig. 194.— Fatty Infiltration of Muscle 1 Muscle Fibres (healthy). - Fat Corpiiscles. DISEASES OF THE IIKAKT ■l()9 of suflioieut exercise coiuluocs very iiurIi to tlu' [irogress of the malady. The auatomical changes resulting from the disease are extremely marked, and very easily recognized by the use of the microscope. The muscular walls are, as in the case of fatty infiltration, commonly paler in colour than the normal structure, and often present a faded yellow or pale-brown tint; the muscle is easily torn or broken down, and has been compared in texture to wet brown paper. Under the microscope the muscular fibres, instead of being well defined with perfectly distinct transverse markings, present a granular appearance owing to the presence of minute granules of fat in their structure, and in some advanced cases every trace of the fibrillated appearance of the normal fibre has become ol)scured, and only a mass of fat granules can bo recog- nized. Symptoms. — It is well known to pathologists that fatty degeneration may advance to a considerable extent without any symptoms becoming ap- parent. An animal may die suddeidy from the disease the existence of which has not been suspected during its life. This will be quite intelli- gible to the veterinarian, as the oc- casional unpleasant sensations which are recognized by the human patient over the cardiac regions would find no expression in the horse. Occa- sional attacks of what in the human subject is described as " angina pec- toris" may occur in the horse, but would either be, as is usually the case, unnoticed, or, if observed, would be referred to an attack of colic or probablv a spasm of the diaphragm. Williams, in his book on llw Practice of Vetennary Medicine, records one case which came under his notice, which he considered to be an in- stance of angina pectoris in a well-defined form. The animal was an aged cart-horse, which for twelve months had done very little work, owing to the fact that when he was excited by work or exertion, he suffered extreme pain in the left fore-limb, the mu.scles of w^hich, with the muscles of the chest (pectorals), became violently convulsed. The paroxysm seldom occurred when the animal was at rest, but there was a continual twitching of the muscles, and the animal appeared to dread being approached. ( >ii examination bv auscultation, a loud cooing or lilowing sound was heard Z 2 Fig. 19.5. — Vatty Dcireneration of Muscle 1 lluscle Fibre (healthy). - - Muscle Fibres infiltrated with fatty granules. 470 HEALTH AND DISEASE over the region of the heart, aud there was a strong impulse indicative of hypertrophy. There was also o]3serva])le a distinct regurgitation of the blood in the jugular vein or jugular pulse. No opportunity in this case was afforded for a post-mortem examination. In some cases of this disease the pulse is remarkably slow, the beats of the heart are generally feeble, irregular, and intermittent, aud while exer- tion increases the frequency of the pulse, it also renders it more irregular, any severe effort soon brings about exhaustion, sighing, and giddiness. Examination of the heart during life reveals certain signs which are said to be characteristic: the impulse is feeble, but is at the same time well defined; the sounds are weak, in the case of the first sound almost inaudible, and in very advanced cases the sounds may be altogether absent; and it is noticed in regard to the feeble pulse that there is some- times only one pulsation to two beats of the heart. RUPTURE OF THE HEART The various alterations in the structure of the heart, arising out of acute myocarditis and the different kinds of degeneration, naturally lead to a weakness and a diminution in the resisting power of the muscular walls, which favours the occurrence of rupture. The determining causes are : violent exertion, falls, excessive excitement, tympanitis, an overloaded condition of the stomach or intestines, &c. Any one of these causes, by obstructing the passage of blood in the larger vessels, increases the pressure on the walls of the heart beyond its power of resistance. It is stated by Zuill that the tear is usually located in the walls of one of the auricles. In our experience it has most frequently occurred in the left ventricle. The occurrence is usually almost immediately fatal; it is said that in falling at the moment of the rupture the horse sometimes utters a piercing cry. AVhen the rupture is slight the ordinary synqjtoms of internal hemorrhage are exhibited. The animal staggers, and, if not sup- ported, falls, the visible mucous membrane of the nostril, mouth, and eye become white and bloodless; there is difficulty of breathing, loss of con- sciousness, and convulsions, and death occurs at varying periods, from a few minutes to several hours. Obviously treatment even in jJi'olonged cases is not likely to be of any use, although it is sometimes effectual in cases of internal hemorrhage from rujjture of the vessels of the liver. Here large doses of opium, with gallic or tannic acid, has sometimes arrested the flow of blood, and the animal has ])artially recovered, but a rent in the walls of the heart is necessarily irremediable. DISKASKS OF 'niK ARTKUIIvS AND VEINS 471 DISEASES UK THE ARTERIES AND VEINS Certain structural cliaiige.s ocoui- in lx)tli arteries and veins owing to intiammatorv attacks and certain forms of degeneration ami injuries occasioned liv the presence of parasites, &(.-. ARTERITIS Arteritis, or inflammation of the walls of an artery, is by no means a rare disease iu the horse. It is usually the result of some irritant acting upon the vessel from within. In man the causative agent is commonly found to be some granulation or vegetation occurring in the structure of the aortic valves. These, when sufficiently large, repeatedly strike the wall of the vessel during the movement of the valves, and excite inflammation in the part struck; or it may result from a portion of blood clot liberated from the interior of a large vessel being carried away and arrested in a smaller one, producing a plugging of the vessel, or embolism. In the horse the disease is most commonly seen in the anterior mes- enteric artery and in that part of the aorta iu immediate proximity to it. It is the result of irritation excited in the vessel by the presence of worms. The parasites Strongylus armatus frequently take up their abode here, and by their presence induce inflammation in the vessel wall. The vessel, which is at first thickened, becomes soft and very much like a piece of wet wash-leather. Its elasticity is impaired or altogether lost, and in consequence it gradually yields to the pressure of the blood stream, and ultimately becomes dilated and forms an aneurism. On the internal surface there is frequently to be found a (juantity of coagulated fibrine, in which the parasites are embedded. Symptoms. — The chief symptoms of this disease are wasting, and diarrhoea, and periodical subacute abdominal pain. The animal is dull and listless, tucked up in the belly, feeds indiflerently, and .sometimes refuses food altogether. If a sharp look-out be kept, small red worms will be found in the excrement. In these cases the partial plugging of the mesenteric artery diminishes the quantity of blood flowing towards the intestine. The function of that organ is therefore imperfectly performed, resulting in periodical attacks of diarrhoea, colic, and a general unthriftiness of the affected animal. The patient sometimes brightens up and appears to have recovered, when recrudescence of the disease occurs, and he goes back in condition, and mav succumb to the disea.se. 472 HEALTH AND DISEASE Treatment. — In all cases of this kind the treatment will succeed in proportion to the injury done to the vessel, and the amount of obstruction to the blood-flow resulting from the degree of dilatation, and the extent to which the vessel has been narrowed by the coagulation of fibrine within it. Very many cases are hopeless, and if they do not die it would be real economy to have them destroyed at once. Some recover, only, however, to be a future trouble to whoever may possess them. These facts should be present to the mind of all persons who are called upon to treat cases of this kind. As we have already indicated, the treatment of this disease is very uncertain. The affected animal should be placed in a well -littered box, and everything should be done to keep up the strength of the body. Food easy of digestion is of the first importance here. Malt meal and linseed, crushed oats and bran, with a very small c^uantity of sweet chaft', all well scalded, will be found for the most part suitable. It is no use trying to destroy the parasites; they are beyond our reach, and cannot be influenced by medicines; but they may sooner or later leave the vessel of their own accord and pass into the intestine. When pain appears it must be combated and controlled by the administration of repeated small doses of ojjium. A little bicarbonate of potash with chloride of sodium may be administered with the food, and repeated small doses of turpentine and aromatic spirits of ammonia should be given in combination with tincture of cinchona as a stimulant and tonic. ATHEROMA (ENDARTERITIS DEFORMANS) This is a disease most commonly seen in the arch of the aorta, or at a little distance posterior to that point. The early stages of the disease are marked by the appearance of small greyish -white spots and patches which are noticed scattered over the interior of the vessel, slightly raised al)ove the surface, and somewhat irregular in size and in form. The inner surface of the aorta is perfectly smooth, but somewhat irregular over the seat of the patches. Tlie endothelium lining the vessel remains for the present quite intact, but the inflammatory new growth situated beneath it raises the endothelium in the direction of the interior of the vessel. In the second stage the cell proliferation, or growtli. to which the patches are due, undergoes a process of fatty change or degeneration, and becomes soft, yellow, and cheese-like, or assumes what is known as an atheromatous condition (,»ft//5,; = meal). DISEASES OF rHK AK THIJIKS AND VEINS 473 The degeuerative pioe-ess may extend to the cells lining the vessel, when they break down, and expose the underlying pasty matter. Should this occur, the hlood in its course backwards washes up the degenerated iutlammatory product and carries it away, leaving the miildle and external coat exposed. In the third stage of the disease the pasty mass, instead of being thus removed, becomes more or less calcified, in which case small bone-like spicules are seen ramifying through the structure of the vessel wall, in some instances completely surrounding it and giving it the appearance of a bony tube (see Aneurism, fig. 196). The efiTect of this disease on the wall of the vessel is seriously to spoil its elastic reaction, and .so interfere with the circulation. When the inflammatory products have undergone the softening process, and become exposed to the blood current, the vessel yields to the pressure from within, causing it to dilate still further, and in consequence an aneurism is formed, or the blood may insinuate itself between the coats of the vessel and cause them to separate, when a dissecting aneurism is the result. When the vessel becomes thin, as is sometimes the case in this form of the disease, its walls may rupture, and death take place more or less suddenly, or the fibrine of the blood coagulated on the diseased surface may fill up the vessel and form a thrombus. If in the second stage of the disease the pasty mass or some adhering clot of fibrine becomes exposed to the current of the blood, and carried away, some portion of it may be arrested in a distant small vessel, estab- lishing the condition of embolism. If this should occur in the lungs, or the brain, or the kidneys, organs specially predisposed to embolism, further, and perhaps fatal, mischief may be the result. THROMBOSIS Both arteries and veins are liable to become more or less completely obstructed during life by the coagulation of blood within them. When this condition occurs it is described as " thrombosis", and the obstructing clot is spoken of as a "thrombus". In the present day, thrombosis in the horse is only of seldom occurrence. Formerly, when blood-letting was resorted to in every conceivable ailment, it was a common affection of the jugular vein, and frequently gave rise to permanent obstruction and obliteration of the vessel. Causes. — The causes of thrombosis are chiefly injuries in one form or another, such as wounds, severe contusion, and stretching; indeed anything 474 HEALTH AND DLSEASK which will excite iiiHammation in the vessel wall or dimiuisli its vitality may determine the coagulation of blood within it. It is also a consequence of degenerative changes in the structure of the vessel, and of arrest of the circulation from aneurism (fig. 196), or any other cause which induces the blood to stagnate. ILIAC THROMBOSIS The most notable example of thrombosis in the horse is that whifh is seen now and again in the iliac arteries — the vessels into wliitli the abdom- inal aorta breaks up beneath the lumbar sjjine, and whose branches are distributed to the hind-quarters and extremities. Causes. — For the most part thrombosis of the iliac vessels is the result of sprain inflicted upon them by some violent backward stretching of the hind-limbs, such as would result when a horse falls short in jumping and slips down the bank of a drain, or when his legs fly liack from under him, or "spread-eagle", while drawing a heavy load over a slippery surface, or out of deep heavy ground. The writer has also known it to be occasioned in the course of the struggles of a horse while cast in a railway box, and in another instance the disease followed upon a hunter being " hung up" across a gate. In all these positions there would be sudden and severe stretching of the vessels and injury to their coats. Symptoms. — The symptoms of iliac thrombosis will vary with the stage of the disease, but, when well established, they are very diagnostic. At first the patient displays slight stiffness of one or both hind-limbs, more especially on rising from the recumbent posture, or when fii'st led out of the stable. This, however, will pass away with a little exercise, to re- appear again from time to time in a more and more marked form. It may be accompanied by slight swelling of the limbs. As the arteries become more and more blocked, and the circulation obstructed, the legs are found to be cold, and the large veins are distended. This distension of the veins results from the absence of force to move on the blood within them, con- sequent upon the blocking up of the arteries, and is most strikingly seen during rest. When the animal is made to move, the blood disappears from the veins, and returns but slowly. The horse's movements ax'e observed to be somewhat unsteady behind, especially during work. In the more advanced stages of the disease exertion brings on a rolling gait behind, and, if continued, results in paralysis of the posterior part of the body At this time the animal breaks out into a profuse perspiration, the breathing is hurried, the muscles quiver, and the pulse is much acceler- ated. In some cases the affected animal strikes the belly, looks round to the flank, and shows signs of acute pain, as if the subject of colic. Plate xxxm THROMBOSIS Fig. I. A. Circumflex artery of ilium. B. External iliac ariery. c. Internal iliac arter)- with Thrombus in silu. D. Thrombus. Fig. 2. Jugular Vein. A, A. Phlebolilhs in silu. B, B. Phleboliths removed, c. Phlcbolith in section. DISEASES OF THE ARTERIES AND VEINS 475 After a short period of rest the symptoms subside, and the horse resumes his normal condition, and will most likely continue in apparent good health until the exertion is again repeated. Although the symptoms described are very indicative of iliac thrombosis, the diagnosis may be rendered still more complete by a careful manipulation of the affected vessels. In this connection it will be remembered that the iliac arteries are to be found striking oft' right and left beneath the lumbar spine, and quite within reach of the hand when pushed well forward into the rectum. In carrying out this examination the hand and arm must be well anointed with oil or vaseline, and after entering the bowel the arm is turned so that the palm is presented upward ; the fingers are then directed to that part of the spine where the loin joins on to the quarters, immediately beneath which the great iliac vessels — two on either side — will be felt branching oft' right and left from the posterior aorta. When healthy, they are found to pulsate forcibly with each beat of the heart, and to be distinctly compressible, though always tense. When, however, they are filled with coagulated blood and rendered solid, as in this disease, the pulsation is no longer felt, and the vessels become hard and unyielding. If they are not completely blocked a slight pulsation may be felt, as a thin stream of blood passes over the clot, but the affected vessels in any ease will have lost their pliancy, and will offer very decided resistance to deep pressure. Treatment in these cases is of no avail. The fibrinous matter plastered over the inner surface of the vessel in successive layers, or free within it and occluding the passage of the blood, cannot be removed, and the animal should therefore be destroyed. THROMBOSIS OF THE JUGULAR VEIN (PHLEBITIS) As already noticed, thrombosis of the jugular vein was a disease of common occurrence in the days of indiscriminate blood-letting and unclean surgical practice as pursued before the advent of antiseptic surgery when phlebitis frequently followed the operation. In more recent years, since the lancet and the fleam have been laid aside, it has become a rare and exceptional ailment. As in arteries, so in veins, thrombosis is the result of degeneration or injury inflicted on the wall of the ve.ssel. It also results when the vessels become varicose or abnormally dilated. In the particular instance under consideration it follows upon the operation of bleeding, or the accidental opening of the jugular vein. But the immediate cause is not perhaps the injury alone, but the introduction into the wound at the time, or 476 HEALTH AND DISEASE subsequent to its occurreuce, of some septic or decomposing matter. A dirty fleam or lancet, a dirty pin, or dirty tow employed to bring the edges of the divided vessel together, are the most likely media by which to infect the wound. Inflammation of the vessel having been thus excited, the blood circulating within it is induced to coagulate, and to be deposited on the inflamed surface layer after layer until the passage becomes com- pletely obstructed and the How of blood along the neck on the affected side is arrested in its course towards the heart. Symptoms. — The lips of the wounded vessel are moi'e or less tumefied ■and separated from each other, and the parts around are swollen and painful to the touch. The plugging of the vessel invariably proceeds in an upward direction, where it may be felt for some distance as a hard, cord- like thickening in the channel of the neck. Subsequent changes in the condition of the vessel and its contents will depend upon circumstances. In some instances the wound heals, the plug becomes organized, still re- taining its position in the vein, with which it unites to form a solid cord. Here the general health of the patient is but little imjjaired; since, how- ever, the jugular vein is no longer able to convey the blood back from that side of the head to the heart, the vessels of the face will be inordi- nately distended, the brain will be somewhat surcharged with blood and liable to slight functional disturbances, especially when the head is held in a depending position. This danger will be materially modified after a time, when compensating enlargement of the jugular vein of the opposite side and its tributaries takes place, and their carrying capacity becomes thereby increased. It must be understood that with one jugular vein spoilt the conveyance of blood from the head to the heart will liave to be done for the most part by the other, which, in course of a little time, will widen out and accom- modate itself to the task imposed upon it. Animals having suffered from this disease should not be turned to grass or allowed to eat from the ground. The downward position of the head under the altered conditions of the circulation tends to an accumulation of venous blood in the vessels of the head, resulting in swelling of the lips and tissues of the face, dizziness, and veitigo. Instead of being organized, the plug in the vein may soften and itreak up into a pus- like matter, resulting in the formation of one or more abscesses in the upward course of the swelling. These may break, empty themselves, and heal, perhaps to form again and produce deep sinuous wounds in the track of the vessel. The most serious consequences re- sulting from jugular thrombosis occur when matter from the softened and disintegrated clot finds its way into the circulation. Thereby the blood DISEASES OF THE ARTERIES AND VEINS t77 beoonies poisoned. The septie piuticle.s uie distiihuted over the hody, ;iii Roaring and Whistling. — Eoaring and whistling are defects of respiration, arising out of a diseased condition of some portion of the air- passages, whereby one or the other of these sounds is produced, according to the nature and degi-ee of the obstruction. As usually met with, it is a chronic and incurable disease, resulting from paralysis of the dilator muscles of the larynx. Less frequently it arises from other causes of a temporary character. Causes. — Perhaps no equine afiec- tion has attracted more attention from veterinary authorities than this, and the opinion is universally held by them that in a large measure heredity is re- sponsible for its wide prevalence. Most people, whether interested in horses or not, have had the subject forced upon their attention from time to time in connection with turf cele- brities, and if the hereditary character of roaring had been more generally accepted in the early days of horse- racing there is no doubt that both our thoroughbred stock and their half-bred produce would have been less subject to the malady than they are now known to be. So many celebrated roarers have gone to the stud that persons best acquainted with the stud-book tell us it is difficult to find a thorough- bred horse whose progeny are abso- lutely free of roarers. Be this as it may, the race-horse of to-day is so susceptible that the slightest cough in a favourite animal spreads dismay among owners and trainers, and a large section of the general pulilic not unfrequently share in the alarm. Chronic roaring is generally referable to wasting of the dilator muscles of the larynx, following upon a cold, an attack of influenza, or strangles, or some affection of the chest, all of which appear to have the effect of causing paralysis of the nerve of supply to the parts affected; or it may, and does, come about while an animal is in the best of general health. Numerous dissections prove that the left side of the larynx is almost inAarinl>]y diseased, and the theory is suggested that this nerve (the left recurrent l)raiK'li of the pneumogastric) Fig. 207. — Larynx of a " Roarer" A, Thyro-aryteuoid Cartilage. B, Arytenoid Muscle. c, Crico-arytenoid Muscle. D, Left Arytenoid Muscle (atrophied). E, Left Crico- arytenoid Muscle (atrophied). DISEASES OF TllK I.AKVNX 511 is rendered specially lialile to derangement, in consequence of its having to wind round one of the larger vessels (aorta) emerging from the heart before ascending the neck. This conclusion may or may not he the correct one, but the fact remains that the right nerve, which does not take this course, is seldom or never art'octed. ^licroscopic examination of the nerve trunk has failed to elicit any information as to the intimate cause of the paralysis, as no change in the structure of the fibres is obser\'able, and we are left to assume that whatever interruption there may have been in the nerve current during life it was not of this nature. In its chronic form roaring prevails in males to a much greater extent than in females, and more frequently in stallions than geldings. It is seldom or never seen in ponies under 14 hands, and the liability to the di.sease increa.ses with the height of the animal and the length of neck. Acute Roaring. — We have hitherto spoken of the one jjrincipal cause of iDariiig. l)ut, as we have already pointed out, there are others of a less serious character, and some of them amenable to treatment. It will be understood that any obstruction to the free ingress and egress of air in the respiratory passage, and especially that portion of it which extends from the nostrils to the lungs, may have the effect of producing a roaring noise. A horse will roar when any tumour or obstructive thickening exists in the nasal chambers, or from any undue pressure on the wind- pipe. Roaring may also be induced by pressure on the larynx, by an accumulation of "matter" in the guttural pouches, by an enlargement of the glands of the throat, or by a spasmodic contraction of the muscles. Moreover, it may, and does, too frequently result from distortion of the larynx following the abuse of the bearing rein, but whetlier this is the explanation or not it is difficult to say. Symptoms. — That grunting is a common accompaniment of roaring is so well known among horse-dealers that they may be seen, in auction sale-yards and other confined places, threatening the animals with a stick to see if thev grunt with fear, and pinching the throat to provoke a cough, the quality of which is in a certain measure, and to an experienced man, a guide to the existence of the disease. Though roarers very frequently have this deep cough, which is a mixture of groan and cough, there are many horses only moderately affected with the malady, who do not, and will not, cough when the larynx is pressed, as there are also whi.stlers who do not grunt on a feint being made to strike them. It has also to be borne in mind that many hor-ses of nervous temperament, and others when out of condition, will grunt on being threatened with a stick, although perfectly sound in the wind. In this affection the patient, while at rest, .shows no symptoms, nor 512 HEALTH AND DISEASE are any awakened, save in bad cases, in the slow paces, and it is not until the animal is galloped, or, in the case of a harness-horse, confipelled to draw a load uphill, or move at a quick pace, that the respiratory trouble becomes apparent. Paralytic roaring usually comes on gradually, and shows but little variation in its severity, and in this respect it difters from spasm of the larynx, which is sudden in its onset, remains only for a brief period, and as suddenly disappears. Treatment. — If roaring is the result of paralysis of the laryngeal muscles treatment is not hopeful, and to steady its further progress and palliate the symptoms is as much as we may look for. Various attempts, surgical and otherwise, have been made to afford relief to the disabled organ. The most recent of these consisted in the removal of that part of the larynx (arytenoid cartilage) over which the muscles had ceased to exercise control, and whose displacement constituted the immediate cause of obstruction to the ingress of air in the act of breathing. Although the operation referred to cannot be said to have been followed by an encouraging measure of success it cannot be regarded as an unqualified failure, as in the hands of the writer it has had the effect in several instances of restoring useless animals to a state of usefulness. The method most commonly adopted for aiding respiration in these cases is that of inserting a tube into the windpipe about one-third of the distance down the neck. Through this artificial channel respiration can V)e effi- ciently carried on without tlie objectionable noise and premature distress resulting from the disease, and by its use the animal's services may be considerably prolonged and his comfort under exertion very materially enhanced. It is, however, at the best an unsightly ex^Jedient, and not altogether unattended with pain, while sooner or later the irritation in- duced by the tube will provoke an outward or inward growth of " proud flesh", rendering a further operation necessary, or maybe the destruc- tion of the animal. All horses suffering from this disease should be kept in high condition. Throwing them out of work and " letting them down" adds considerably to the embarrassment of the breathing, if it does not also expedite the disease. 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