Operations on Animals

Operations on Animals are performed: 1) for experimental purposes, 2) as an aid in teaching, and 3) for therapeutic and zootechnical purposes. In the first case, they serve as one of the main methods for studying problems in physiology and biology; in the second, they help the medical student surgeon acquire the necessary operative skills for subsequent independent operations on humans; and in the third, they are part of the scope of operative veterinary medicine and zootechnology. Depending on the objectives pursued, operations performed on animals vary. Similarly, the animals operated on also vary depending on these same objectives. For experiments and teaching, small animals—dogs and rabbits—are the most convenient and therefore most frequent subjects of operations. Among therapeutic and zootechnical operations, those on dairy and meat cattle and horses are most important for the economy, and therefore they are most common in veterinary practice. Physiological operations on animals have been performed for a long time, taking the form of vivisections. Harvey established the law of circulation and so on by this method. With the help of these operations, the functions of organs are studied in two ways: direct observation and indirectly by artificial exclusion of the organ. The first principle forms the basis for studying the glands of external secretion, excretory organs, and intermediary metabolism; the second, for the glands of internal secretion and the nervous system. The study of glands of external secretion is achieved by creating chronic fistulas. With the help of these fistulas, the secretion of the gland is obtained. The operation for creating a chronic fistula of the salivary glands consists in bringing the ducts of the parotid, lacrimal, and mucous glands of the dog to the outside, along with a portion of the oral mucosa, followed by its implantation in a skin wound on the cheek or chin. With the help of an esophageal fistula created 8 y* by esophagotomy, Pavlov was able to carry out the so-called sham feeding, in which swallowed food falls out. This operation is used as an adjunct in creating a gastric fistula for studying the 'first phase' of digestion, which consists in the reflex appearance of gastric juice. In its simplest form, the method of creating a chronic gastric fistula consists in suturing the wall of the stomach fundus to an abdominal wound and inserting a cannula into the stomach, which is brought out. For obtaining pure juice, it was proposed to isolate the pyloric part of the stomach or to use wedge-shaped excision of the fundus with subsequent formation of the so-called 'small stomach,' and to suture the fistula opening into the skin wound. The most rational, but technically more complex, is Pavlov's method, which, when excising the stomach fundus and making a longitudinal incision from the pyloric part toward the entrance, leaves a bridge of serous, muscular, and submucosal tissue to connect the large stomach with the small one, thereby preserving the secretory nerve fibers. The operation for creating a fistula of the small intestine according to Thiry (1 hiry) consists in excising a segment of the intestine without damaging its mesentery, sewing one end of the excised segment shut, then immersing it in the abdominal cavity and suturing the other end into a skin wound. Pavlov modified Thiry's method: preserving the seromuscular layer with a longitudinal incision, he made only a transverse incision of the mucosa, sewing it shut at both ends. Thus, the secretory nerves passing through the intestinal wall remained undamaged; the possibility of the secretion flowing out was achieved by inserting a metal cannula into the sutured segment. The operation for creating a fistula of the pancreas in its simplest form consists in excising a segment of the duodenum with the site of exit of the duct of the gland and subsequently suturing this segment to the skin. To obtain inactive juice not in contact with enterokinase, one can later excise the segment of intestine implanted in the skin, at the same time draining the duct, as proposed by Babkin. The study of bile secretion is carried out with the help of a gallbladder fistula. To obtain all the bile, this method is combined with ligation of the common bile duct; for studying the exit of bile into the duodenum, an operation for creating a bile duct fistula is performed, which in details corresponds to the operation for creating a pancreatic fistula. An example of an operation intended for studying excretory organs is the creation of a bladder fistula, first performed on rabbits by Keler. Orbeli developed a method for bringing out the ureters with a small segment of the bladder, suturing each of them separately to the skin on either side of the nipple line. An example of an operation intended for studying intermediary metabolism is the Eck-Pavlov fistula (Eck). To determine the role of the liver in metabolism, Eck and Pavlov proposed to exclude portal circulation from the liver by connecting the inferior vena cava with the portal vein with a suture, and then ligating the latter at the liver hilum. For the same purpose, London proposed anastomosis of the portal and hepatic veins. The functions of the glands of internal secretion were studied by their removal. Mering and Minkowski, by removing the pancreas in a dog _?, caused the appearance of symptoms of diabetes in it. The works of Reverdin and Kocher showed that complete removal of the thyroid gland in animals causes infiltration of connective tissue with mucus, and removal of the parathyroid glands causes tetany; Brown-Séquard, however, after removing the adrenal glands, observed the death of the animal with symptoms of nervous disorders and weakening of muscular activity. Similarly to the study of the functions of the glands of internal secretion by removal of organs, the study of the function of the central and peripheral nervous system proceeded. The study of animals in which the cerebral hemispheres were removed determined the role played by these hemispheres in the functions of the entire nervous system. For the first time, Holtz succeeded in keeping alive a dog from which he had removed both hemispheres. A dog without cerebral hemispheres, having lost all higher manifestations of psychological characteristics and retaining only certain functions related to the environment (maintaining equilibrium, coordination of movements, and the ability to express emotions), was a true reflex animal. To determine the functions of the cerebellum, Flourens removed it in pigeons, and Luciani in dogs, both researchers observing disturbances in coordination of movements in their experiments. Flourens, by cutting the semicircular canals of the pigeon's inner ear, caused disturbances in its equilibrium and so on. Educational operations on animals were first used in Germany. In the early 20th century, practical courses for physicians in operative technique on living dogs (Schmiden's course and others) were organized in Berlin. In our country, educational operations on animals were first performed for medical students at the Military Medical Academy in 1911, and now they are almost mandatory in all medical institutions as a supplement to operating on cadavers, and in this respect the dog has proven most convenient, both in terms of ease of acquisition and simplicity of postoperative care, and the size of certain organs, for example, the intestine. Among operations on dogs, especially recommended for educational purposes, can be named: ligation of the femoral artery, resection of a rib, tracheotomy, intestinal suture, gastrostomy, anterior gastroenterostomy, resection of the intestine, resection of the stomach, removal of the gallbladder, removal of the kidney, and trepanation of the skull. Ligation of the femoral artery is performed at the Poupart ligament, where the artery is free of large collaterals. Resection of a rib is performed according to general rules, but necessarily without opening the pleural cavity, because in dogs both pleural cavities communicate with each other through a series of openings in the anterior mediastinum, and a unilateral pneumothorax easily turns into bilateral. Tracheotomy in a dog is performed more easily than in humans, since it lacks the isthmus of the thyroid gland, and the latter is represented by two isolated lobes located on either side of the trachea. As for intestinal operations, they are even more difficult in a dog than in humans, and therefore a surgeon who has mastered the operative technique on animals is usually surprised at the ease of performing such an operation on a human for the first time. Performing gastrointestinal operations for a student surgeon is essential, since similar operations on cadaveric material can only serve to clarify anatomical-topographical relationships. Access to the stomach and intestine of the dog is opened by a layered incision along the white line of the abdomen from the navel to the xiphoid process, stopping 4-5 cm short of it so as not to injure the diaphragm. From the anatomical peculiarities of the dog during gastrointestinal operations, one should not forget about the absence of the gastrocolic ligament, which makes posterior gastroenterostomy pedagogically less demonstrative, as well as about the abundance of loose submucosal tissue in the stomach and intestine of the dog, which allows, without opening the lumen of the stomach and intestine, to separately incise the serous and muscular membranes from the mucosa.

In all other respects, the technique of gastrointestinal operations is the same. - The incision for gallbladder removal is made along the white line or to the right of it along the edge of the right costal arch. The cystic artery is not isolated separately, as is done in humans, but is included in general ligatures, after which the duct and artery are severed between them. - For extraperitoneal removal of a dog's kidney, it should be remembered that unlike in humans, the kidney capsule is fused with the peritoneum, and therefore any attempt to isolate the kidney without first performing decapsulation results in opening the abdominal cavity. Veterinary operations are diverse and depend on the species of animal undergoing the operation. They are divided into cosmetic, zootechnical, and therapeutic operations. Cosmetic operations include, for example, amputation of ears and tails, as well as tail tenectomy in dogs. Zootechnical operations include: castration of pigs, undertaken for economic purposes to promote fat accumulation; castration of cows to extend the lactation period, increase quantity, and improve milk quality; castration of rams and boars to promote fat deposition in them. The operation of castrating animals is the most common in veterinary practice. Stallions and bulls are castrated to suppress sexual desire that interferes with their use as working animals. -- The general principles of operative-therapeutic technique in animals do not differ from the same principles of operating on humans. Only the details and individual operations differ, which depends on the anatomical-topographical features and specific surgical diseases observed in animals. Operations of this latter type include, for example, the surgical treatment of whistling asthma in horses. Among the most common therapeutic operations in veterinary practice, which are also performed on humans, it is necessary to mention: various types of tenotomies and neurectomies in horses, trepanation of the cranial sinuses in them as well as in large ruminants; operations for inguinal and umbilical hernias, removal of prolapsed rectum and uterus in dogs, horses, large ruminants, small ruminants, and pigs; the operation for cataract removal in dogs. -- Anesthesia in O. n. zh. is used both general and local. A horse can easily be anesthetized by applying to its nostrils a compress soaked in chloroform. To avoid irritation of the mucous membrane in this case, the nostrils and the end of its muzzle should be abundantly smeared with vaseline. To shorten the period of excitement and prevent collapse, preliminary injection of atropine-morphine is recommended. Intravenous injection of chloral hydrate to horses is very convenient. Anesthesia by inhalation of chloroform or chloral hydrate is not suitable for animals whose meat must be consumed as food in case of surgical failure. Sheep absolutely cannot be chloroformed, as they usually die from chloroform anesthesia. General anesthesia for small animals is preferably ether. As for local anesthesia, in veterinary practice for operations on large animals, freezing with cooling mixtures is used, as well as circular constriction if the operation is performed on the limbs. For operations on small animals, cocaine anesthesia is used according to general rules, taking into account the weight of the animal.

K. Baryshnikov..