1.Cats usually like the house in which they live better than they like the people who live in it.They will leave a kind mistress and go back to their old homes.But if we are kind to our dogs，they will love us，and will follow us all over the world.
2.Dogs were once wild animals.Wild dogs are still found in some countries.
They hunt in packs①，and
feed on the flesh of the animals which they kill.
3.The dog has a long pointed nose or muzzle.Ifa dog’s nose feels cold andWILD DOGS（野狗）wet，this shows that he is quite well；when he is ill，his nose feels hot and dry.
4.Under the loose skin of the dog we can feel his strong backbone，and also the muscles or lumps of flesh by which he moves his legs and all the other parts of his body.
5.The dog has five toes on each of his fore-feet，but only four①Packs，numbers together.
toes on each hind-foot.Each toe has a strong nail or claw，with which the dog can scratch and dig in the ground.Perhaps you have seen him digging a hole，and burying in it the bones which he has not finished eating.
6.The cat has sheaths or cases into which it draws back its claws when they are not wanted.The dog has not.For this reason，a dog‘s claws are never sharp like those of thecat.
7.The dog cannot walk so quietly as the cat；for although his feet have soft pads under the toes，the points of thehard claws strike against the ground，and make a noise when he walks or runs.
8.The dog has bright and knowing①eyes，but hecannot see at night so well as the cat can.The pupil，or little black space in the middle of each eye，is never so large as that of the①Knowing，wise-looking.
cat.Pussy chases the mice by night，but the dog hunts only in the day-time.
9.There is another difference between the dog’s eye and the cat‘s.Do you remember reading in the previous lesson that in a bright light the pupil of the cat’s eye closes until it is only anarrow slit①？The pupil of the dog‘s eye is not like this.It isalways round，however bright the light may be.
10.Notice the dog’s teeth.How white and strong they are！All his teeth are sharp and pointed.He has seventeen teeth in the upper jaw，and nineteen in the lower jaw.
11.The dog has two long teeth in each jaw for seizing his prey.
The other teeth are for tearing the flesh and crushing the bones on which he feeds.The dog lives chiefly on flesh，and he has no flat teeth for grinding his food，like those of grass-eating animals.
12.Grass-eating animals like the cow can move their jaws sideways as well as up and down，in order to grind their food well；but flesh-eating animals like the dog can only move their jaws up and down.
13.The tongue of the dog is long and smooth.It is very different from the rough tongue of the cat.When a dog is very hot，he always lets his tongue hang out of his mouth，for it is by his tongue that he sweats or perspires.
①Slit，a long，narrow opening or cut.
SUMMARY
The dog，when kindly treated，is a very loving animal.He has a long，pointed nose or muzzle.He has bright and knowing eyes；but he cannot see so well at night as the cat.He has five toes on each fore-foot，but only four on each hind-foot.The dog has strong but blunt claws for digging in the ground.His teeth are very strong.He has four long teeth for seizing his prey.The dog‘s tongue is long and smooth，and he perspires by means of it.He lives on flesh.All dogs were once wild animals.Wild dogs are still found in some countries.
【中文阅读】
1．猫非常重视生活的屋子环境，相对就不那么重视屋子里的人。猫可能会离开和善的女主人，回到自己原来的住处。不过，我们要是好好地对待自己的狗，狗就会爱我们，跟着我们走到天涯海角。
2．狗以前曾经是野生动物。现在的一些地区还能找到野狗。野狗成群地狩猎，以杀死的动物为食。①3．狗的鼻子又长又尖，学名叫“口鼻部”（muzzle），狗在健康的时候，鼻尖是又湿又冷的；病了，鼻子就变得又热又干。②4．狗的皮肤比较松弛，皮肤下面，我们能摸到强壮的脊椎骨，还有大块的肌肉（muscles或flesh），狗就用这些肌肉，活动四条腿，也活动身体的其余部分。
5．狗的每条前腿上都有五个脚趾，但是后腿上只有四个脚趾。每个脚趾都长着一个坚硬的“指甲”或者“爪”，狗可以用爪子抓地、刨地。也许你见过狗在地上挖洞，把没吃完的骨头埋在洞里。
6．猫在不用爪子的时候，可以把爪子缩回到“爪鞘”或者“爪套”里面，这个部分的学名是“球套”。狗却没有这个部分，所以狗的爪子始终不会像猫一样锋利。
7．狗走路的时候，不像猫那么安静，因为狗的脚尽管也有软垫，但也是硬硬的爪尖会碰着地面，狗在走动或者跑动的时候就会发出声音。
8．狗长着明亮的、善解人意的眼睛，但晚上看东西不像猫看得那么清楚。狗的瞳孔，也就是每只眼睛中间的小黑点儿，始终不会像猫一样大。小猫咪可以在晚上追老鼠，但是狗只在白天才狩猎。
9．狗和猫的眼睛还有一处不同。你还记得吗？在前面的课文中猫眼睛的瞳孔，在强光下，会眯得只剩一条缝。狗眼睛的瞳孔却不会这样，不管光线怎么强烈，瞳孔一直是圆的。
10．注意狗的牙。这些牙齿好白好硬啊！狗的牙齿全都是很尖很锋利的，上腭有17颗牙齿，下腭有19颗。③11．狗的上下腭各有两颗长长的牙齿，用来咬住猎物。另外的牙齿用来把肉撕裂，把骨头碾碎，狗就吃这些肉和骨头为生。狗的食物主要是肉，没有用来磨碎食物的扁平牙齿，这一点跟食草动物不一样。④12．牛一类的食草动物，上下腭除了上下活动，还可以横向活动，这样可以把食物磨得很碎；但是，食肉动物的上下腭，只能上下活动。
13．狗的舌头又长又光滑，跟猫的粗糙的舌头很不一样。狗在非常热的时候，总是把舌头伸到嘴外面，因为狗是用舌头出汗或者排汗的（英语的两个动词分别叫sweat和perspire）。⑤译注①狗属于“哺乳纲”“食肉目”“犬科”“犬属”“狼种”“家犬亚种”，是从狼驯化来的。至少14000年以前，狗就已经被人类驯化了。狗的英语dog，可以泛指所有犬科动物，包括狼在内，大概这也是原文里提到“野狗”的原因。现在不存在与狗完全同种的“野狗”，只有狼。汉语名称有“野狗”的犬科动物，包括“非洲野狗”、“亚洲野狗”（豺）和“澳洲野狗”。电影《狮子王》里面的鬣狗，虽然名字里有“狗”，但其实跟猫的关系更近。另外，汉语里的“野狗”有时候指流浪狗，这就不是生物学的分类概念了。
②这个说法不准确。当时狗有一种流行病叫犬瘟热，其症状之一就是狗鼻子和脚垫发热发干，因此狗鼻子如果湿冷，表示狗没有得犬瘟热。现在有了疫苗，犬瘟热就少得多了。狗在早上醒来的时候，鼻子可能又热又干，但这是完全正常的情况。但是，狗鼻子如果一直又热又干，的确可能是疾病的征兆，要去看兽医。
③原文可能有误。难道作者碰巧观察了一条有残疾的狗？长头犬的上腭有20颗牙齿，下腭有22颗，一共42颗。当然，这是发育正常的情况，狗的牙齿数目也和人一样，会随着个体不同而变动。
④实际上，家犬的食性很杂，虽然以肉食为主，但也经常吃各种植物。
⑤这个说法也错了。狗的舌头上没有汗腺，只有唾液腺。狗的舌头分泌的液体是唾液，不是汗。原文里的说法，早在1899年就让《不列颠医学杂志》纠正了。狗出汗主要是通过脚垫，但狗调节体温的主要手段，确实是喘气和用唾液湿润口腔，还包括让面部和耳朵的血管扩张。
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