May be killed by drowning in dilute methylated spirit, or by chloroform. Take a recently-killed frog, and examine a drop of its blood, spread out on a glass slip, under the microscope; compare it with your own. Before using the high power, put a cover glass over the object, of course. Scrape the roof of the mouth of the frog gently, to obtain ciliated epithelium; and mount in very weak salt solution-- the cilia will still be active. Squamous epithelium may be seen by the student similarly scraping the interior of his own cheek. Take a piece of muscle from one of the frog's limbs, tease out with needles upon a glass slip, and examine. To see the striations clearly, the high power will be needed. Compare a piece of muscle from the wall of the alimentary canal. Similarly examine nerve and connective tissue. First Dissection.-- Pin out the frog in a dissecting dish, ventral surface uppermost, and cover with water. Open up the skin along the mid-ventral line. Note the large sub-cutaneous lymph spaces, the pelvic and pectoral girdles, and the anterior abdominal vein. Cut into the body cavity on one side of this latter, cut across in front of where the vein dips down to liver, and peel the body wall away from it. The xiphisternum will probably be cut in this operation. In early spring the females are greatly distended with ova, and the greater portion of the ovary may, with advantage, be removed. The oviduct is dead white then, and larger and much more in evidence than the (pinkish) intestine even. Turn over the viscera, and compare with Sheet 11; one lung is often found greatly inflated, and then projects back into the body cavity; the stomach is, in some cases, pushed forward and hidden behind the shoulder girdle. Observe the allantoic bladder, the spleen, gall bladder, portal vein, and pancreas. By squeezing the gall bladder gently, the bile duct will be injected with bile, and will be apparent if the stomach is turned over. The oesophagus, just in front of the stomach, should be cut through, and the rectum, and the mesentery and alimentary canal supported by it, removed. This will expose the urogenital organs. (Vide Figures given.) These vary greatly, especially in the females, at different seasons. The condition figured would be seen in late autumn, or winter. In spring females are often found copulating with males, and then the ovary itself is inconspicuous, while the lower part of the oviduct is enormously distended with ova, so as to be mistaken sometimes for the ovary by those who fail to note that the ova are enclosed by a thin semi-transparent skin (wall of oviduct). The vena cava inferior is seen between the kidneys and the renal portal vein beside the ureter. Cutting through the mesentery supporting the kidney laterally, the dorsal aorta is exposed, and on either side of it the sympathetic chain and rami communicantes, often tinged with black pigment. This black pigment is a frequent but variable feature of the frog's