Image from page 965 of “British medical journal” (1857) – more Marine Life goodness curated by www.SardineRunPE.co.za
Image by Internet Archive Book Images
Title: British medical journal
Year: 1857 (1850s)
Authors: British Medical Association
Subjects: Medicine Medicine
Publisher: London British Medical Association
Contributing Library: Gerstein – University of Toronto
Digitizing Sponsor: University of Toronto
Click here to view book online to see this illustration in context in a browseable online version of this book.
Text Appearing Before Image:
n the embryo, by thenumber of the nerve ganglia,and so on, leeches seem alwaysto have thirty-four such seg-ments. These do not corre-spond with the rings or annula-tions 80 visible on the outside,l)ut a certain number of theseannulations, varying in eachspecies, go to each somite,and so constant aro these num-bers that it would not be verydifficult to represent any givenspecies of leech by a mathe-matical formula.The known species readily fall into two sub-orders:(1) The lihynchohdellae, which are marine and fresh-water leeches with colourless blood, with no jaws, andvi-ith an extensile proboscis; and (2) the ArhiinchobdeUoc,wiiich are all fresh-water or terrestrial, with red blood,and generally with jaws. There is no extensile proboscis,and the anterior surUer has a ventral aspect, and is in noway distinct from the body. There are always in tliisgroup seventeen pairs of nephridia. We shall have mostlyto do with the latter sub-order.Hirudo medicinalis, the medicinal leech, is foimd iu
Text Appearing After Image:
Fig. 1.—Hirttilo meihcin-nlis; about life size. 1.ftloutli; 2. posterior sucker;3, seusorj papiUao on theanterior annulua of eaclisegment. Tlie remainingfour annuli wliicll make upL-at;h true segment are indi-cated by the markings onthe dorsal surface. stagnant waters throughout Europe and the western parts of Asia. It is rather commoner iu the southern partti of Europe than in the north. It used to be common enough in England, where it was bred, but already 100 years ago its numbers were diminishing. In a treatise on the Medi-cinal Leech, published by.J. R. Johnson in the year1816, he records formerlythe species was very abun-dant in our isi.and, but fromtheir present scarcity owingto their being more in re-r[uest among medical men.and to the rapid improve- -ments which have of lateyears takeo place in agricul-ture, particulaily in thedraining and cultivation ofwaste lauds, we are obligedto receive a supply from theContinent, chiefly from Bor-deaux and Lisbon. In histime he conside
Note About Images
Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability – coloration and appearance of these illustrations may not perfectly resemble the original work.