POMPHUS 



1157 



PONTAL 



more common in women, but is met with chiefly in 

 adult and middle life. By some it is considered a 

 disease of the sweat-glands, by others not. The dis- 

 ease is curable, but tends to recur. 2. Sometimes 

 used as a synonym for Pemphigus. 3. Zinc oxid, 

 called Flowers of Zinc, and Philosophers' Wool. 

 Pomphus {pom'-fus) {jrou^oq, blister: //., Pomphi\ 

 il; Urtica ; a circumscribed edema of the co- 

 rium, producing a flat elevation of the epidermis at 

 that point ; it is usually the result of angio-neurotic 

 irritation. Pomphi vary in size from a pin's head to 

 a goose's egg, are of irregular outline, and of a whitish 

 color with a pink areola. They are evolved rapidly, 

 and usually last only a few hours or days. 

 Pomum (py - mum) [L., //., Poma]. Apple. P. 

 adami [L., Adam's apple] , the ridge or prominence in 

 the front of the neck caused by the projection of the 

 thyroid cartilage. It is most marked in males. P. 

 quercina, nut-gall. 

 Ponceau f>on-so / ). See Pigments, Conspectus of. 

 Pond's Extract. See Hamamelis. P.'s Recipe, a 

 recipe for varnish to preserve sphygmographic and 

 cardiography tracings. Alcohol, one pint ; gum san- 

 darac, three ounces; castor-oil, half ounce. Mix. 

 Ponding pond'-ing) [ME.,/o«(/, a pond]. The ac- 

 cumulation of liquid as in a pond. P. of the Liquor 

 amnii, the collection of a considerable amount of 

 liquor amnii above the presenting part of the fetus 

 after the membranes have ruptured in the second 

 stage of labor. 

 Pongamia ( pon-ga' '-me-afi) [E. Ind. pongani\. Agenus 

 of East Indian trees. Kurung oil is the oil expressed 

 from the seeds of P. glabra, native to India, China, 

 and Australia. It is recommended in parasitic dis- 

 eases of the skin, and is efficacious in pityriasis versi- 

 color, herpes, and rheumatism, and is useful in lepra. 

 Unof. 

 Ponos (po / -nos) [toi>oc, pain]. A chronic febrile dis- 

 ease endemic on the Greek islands of Spetzia and 

 Hydra. The disease bears some resemblance to 

 pseudoleukemia and to tuberculosis. 

 Pons [pons, bridge]. A process or bridge of tissue 

 I connecting two parts of an organ. P. cerebelli. Same 

 ' as P. varolii. P. hepatis, the hepatic substance some- 

 i times extending from the quadrate to the left lobe of 

 the liver. P. tarini, the posterior perforated space, a 

 mass of gray substance lying behind the corpora albi- 

 I cantia and joining the crura cerebri. It helps to form 

 ! the floor of the third ventricle. P. varolii (or simply 

 I Pons), a convex white eminence situated at the base 

 of the brain, behind its center. It is placed cephalad 

 of the oblongata, ventrad of the cerebellum, and caudad 

 of the cerebrum, and is connected with all three. It 

 rests upon the sphenobasilar groove ; it is quadrate in 

 outline, about 25 cm. wide antero-posteriorly, and is 

 marked on its ventral surface by a longitudinal groove 

 for the lodgment of the basilar artery. It is contracted 

 \ laterally on account of the closer aggregation of its 

 ■ fibers, which converge to form the middle peduncles of 

 the cerebellum. Its cephalic margin is convex and well 

 defined, and arches over the crura. From the cepha- 

 lad surface of the pons, a little ventral, arises the fifth 

 or trigeminus nerve. In structure the pons consists 

 chiefly of nerve-fibers, but it contains also areas of gray 

 matter, the pontine nuclei. On section it consists of 

 two portions, a dorsal and a ventral. The latter con- 

 tains transverse commissural fibers and is traversed by 

 the ventral pyramids of the oblongata. The pyramidal 

 fibers in the caudal half of the pons are collected into 

 two closely-packed groups of bundles invested in front 

 and behind by a layer of transverse fibers ; higher up, 

 above the middle of the pons, the pyramidal tracts be- 



come separated by the penetrating transverse bundles 

 into a number of fasciculi. The presence of the pyra- 

 mids thus gives rise to three sets of fibers — the ven- 

 tral or superficial, the dorsal or deep, and the middle or 

 penetrating. Interspersed in the gray matter occupying 

 the interstices of the ventral portion of the pons small 

 multipolar cells are found. The dorsal portion of the 

 pons consists largely of gray matter which is continued 

 up from below, especially the formatio reticularis 

 and the dorsal tracts of gray substance. In places 

 the gray matter is grouped to form the nuclei of the 

 fifth, sixth, seventh, and eighth nerves. In the lower 

 part of the pons there is a small, folded gray lamina, 

 distinguished as the superior olivary nucleus. It is en- 

 closed by some transverse fibers known as the trape- 

 zium . A group of darkly-pigmented cells is found in 



Pons and Medulla. Anterior Aspect. 



1. Infundibulum. 2. Tuber cinereutn. 3. Corpora albtcantia, 

 or niammillaria. 4. Cerebral peduncle. 5. Pons varolii. 6. 

 Middle cerebellar peduncle. 7. Anterior pyramid. 8. De- 

 cussation. 9. Olivary body. 10. Gray tubercle of Rolando. 

 11. Arciform fibers. v2. Superior extremity of spinal cord. 

 13, 13. Denticulate ligament. 14. Spinal dura mater. 15. 

 Optic tract. 16. Optic chiasm. 17. Third nerve. 18. Fourth 

 nerve. 19. Fifth nerve. 20. Sixth nerve. 21. Facial nerve. 

 22. Auditory nerve. 23. Nerve of Wrisberg. 24. Glosso- 

 pharyngeal nerve. 25. Vagus nerve. 26, 26. Spinal acces- 

 sory' nerve. 27. Hypoglossal nerve. 28. 1st cervical pair. 

 29. 2d cervical pair. 30. 3d cervical pair. 



the floor of the fourth ventricle ; collectively, this is 

 visible to the naked eye as a dark area, known as the 

 substantia ferruginea ; seen through the floor of the 

 fourth ventricle, this area appears of a bluish-gray 

 color, whence the name locus cceruleus. Mesad 

 of the substantia ferruginea lies an angular tract 

 of white matter, the posterior longitudinal bundle, 

 which is a continuation upward of the ventral ground- 

 bundle of the cord. The pons is developed from that 

 part of the third brain-vesicle known as the hind- 

 brain or epencephalon. 

 Pontal (pon'-tal) I pons, bridge]. Same as Pontile. 



