Physiology practicums : explicit directions for examining portions of the cat, and the heart, eye, and brain of the sheep, as an aid in the study of elementary physiology.

  • Wilder, Burt G. (Burt Green), 1841-1925.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Physiology practicums : explicit directions for examining portions of the cat, and the heart, eye, and brain of the sheep, as an aid in the study of elementary physiology. Source: Wellcome Collection.

Provider: This material has been provided by the Gerstein Science Information Centre at the University of Toronto, through the Medical Heritage Library. The original may be consulted at the Gerstein Science Information Centre, University of Toronto.

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    with the other hole and note its emergence upon the other lid. These' are the CANALICULI or lachrymal canals. a. Were the adjacent parts retained these two canals would be found to open into a sack, the LACHRYMAL SACK, continuous through the nasal duct into the cavity of the nose. b. If the cat's head has been retained these parts may be traced, though with some difficulty on account of their small size. The ventral end of the nasal duct is just laterad of the ventral turbinal, maxillo-tur- binal, indicated in PI. XVII by the abbreviation Mxtrb. c. Through the passages above described the natural moisture of the eye, keeping the apposed conjunctival services soft, is drained away into the nose and evaporated by the currents of air. Where there is an excess of lachrymal secretion, as from taking cold, from the odor of an onion, or from laughter or crying, part runs over the edges of the lids as tears, and part makes itself apparent in the nasal cavity. d. The orifices of the canaliculi at the margins of the lids are narrow and valvular so that particles of any size do not readily enter. e. The small curved blunt pointed knife called by anatomists syringotome (tube- opener) is used by surgeons in opening up the lachrymal canals, and is called by them canaliculus knife. f. The lids may be cut away with the scissors. # 12. The Cornea and Solera.—On the free surface of the ball the elliptical area in- cludes the CORNEA, transparent during life but rendered opaque by alcohol ; the rest of the surface of the ball is constituted by the naturally white and opaqe SCLERA, commonly called Sclerotic. a. In the natural attitude of the sheep's head the long axis of the cornea is nearly parallel with that of the brain but not with that of the head as a whole. §13. The Caudal Aspect.—Note again the following features more in detail than above (§3). a. FAT and CONNECTIVE TISSUE, in white, irregular masses ; they constitute a cushion for the ball ; during prolonged illness or fasting the fat wastes so that the eye literally becomes sunken. b. In the midst, the white, firm, fibrous OPTIC NERVE. c. The cut ends of the MUSCLES. § 14. The Rectus Muscles.—With the fingers (using the knife-point or tracer sparingly), pulling mostly from the center, tear out the fat and connective tissue so as to separate four muscles, at the four opposite sides of the ball ; these are the RECTI (straight) muscles. Their TENDONS unite to form a continuous sheet, thin but tough, entad of the severed con- junctiva. a. There are two OBLIQUE muscles whose location and attachments are less easily recognized ; see the models and diagrams. b. The superior oblique muscle passes through a fibrous loop at the mesal side of the orbit as through a pulley, and may be exposed if time permits. c. Immediately surrounding the optic nerve is another layer of muscle, but it does not exist in man and may be disregarded. § 15. Demonstration of the Actions of the Rectus Muscles.—Hold the eye lightly between the left index and pollex, the dorsal side up. Grasp the rectus that is attached to the mesal side of the ball, i. e., correspond- ing with the end of the cornea which is partly covered by the plica. Pull the muscle and thus rotate the ball mesad, i. e., inward. Pull the muscle at the opposite side and rotate it laterad, i. e., outward a. Strabismus or squint may be due to either the shortness or undue contraction of one muscle, or to the length or weakness of its an- tagonist. b. With the scissors trim off the rectus muscle and the plica.