In this weeks Parsha, an interesting event takes place, as Aharon and his sons are anointed as the Kohanim ויקרא ח':ל'(). As described earlier (שם פסוק כ"ג), part of that procedure was to put blood on Aharon's ear, thumb, and big toe, and then to do the same for his children (שם פסוק כ"ד). This seems strange. Why would this be done to anoint a Kohein? We know that a king is anointed with oil, but apparently a Kohein is anointed with blood as well as oil. We now have two questions. First, why blood? Second, why is the blood put on the ear, thumb, and big toe?
To understand why blood is used for a Kohein, while a king is anointed with only oil, we must understand what blood represents. Blood represents life. Some say that the Neshomoh is in fact carried in it. In the story of Kayin and Hevel, it was the blood of Hevel that called out - not the bones, not the body, but perhaps the Neshomoh (בראשית ד':י'). Some say that animals don't have a Neshomoh like humans do. In that case, blood must be symbolic of what human beings really are made of, and thus focuses attention on the spiritual side of man.
Oil represents another connection, this one not being between the body and the Neshomoh, but instead, between man and Hashem. Oil is natural; in other words, Hashem made it - not man. We thus see that it has a "connection" to Hashem, but what is it's connection to man? Oil is like spices, in that it is considered to be like one of the "riches" that man can have. In food, oil is considered to be almost as "high" in importance as a spice. Spices are considered "precious" - almost like gold - though not always as expensive. Oil is thus sometimes chosen to represent wealth, and it therefore has a "connection" both to Hashem and to man. Why does the Kohein use oil also? Perhaps it is for the same reason. The Kohein represents a connection to Hashem as well as to man, and he is thus anointed with oil, a substance that represents both these connections, as well as with blood, which focuses upon the spiritual and the inner part of man, the Neshomoh.
Although it may seem like a king is "lower", because he is anointed only with oil, it's actually not that he's lower, but rather that he has a different job. He has to follow the laws of the Torah and relate to both people and to Hashem, but spiritual issues don't always have a direct connection to him, at least in public. He's a leader of men, and not a daily visitor to the Beis HaMikdash. This might be, incidentally, why he writes two Sifrei Torah (דברים י"ז:י"ח). One is to stay "home," and one is to travel with him. He has to know the laws concerning man and his fellow man, as well as those which remind him who is higher than the king, namely Hashem, the King of all kings. But he is not that involved publicly in spiritual matters.
We now must understand why the blood was sprinkled on the ear, the thumb, and the big toe. When we examine what the ear is used for and what the hands and feet are used for, we realize that the ear is for hearing and the hands and feet are for doing. This could correspond to the idea of "Naaseh VeNishma," the famous phrase said by Bnai Yisrael at Har Sinai (שמות כ"ד:ז') committing themselves to listening (with their ears) and doing (with their hands and feet). As for why only the thumb and the big toe, it may be because these organs, like the ear, are what separate man from the animal kingdom. In Sefer Shofetim (א':ז'), we read that seventy kings had their thumbs and big toes cut off. Some Meforshim say that this made them like animals, because most animals don't have thumbs and big toes. As for the ears, there are several opinions as to where exactly the blood was sprinkled. According to the Targum Onkelos, it was the upper part of the ear, according to Rabbeinu Saadyah Gaon, it was the lower lobe, according to the Sifra, it was the center of the ear, and according to the Rambam, both in his Peirush HaMishnayos in Negaim (פרק י"ד משנה ט') and his Mishneh Torah (פרק ב' מהל' מחוסרי כפרה הלכה א'), it was on the inside cartilage just inside the helix of the ear. If we consider that the thumb and big toe are meant to focus on the distinction between man and animals, we'll understand that the lower lobe seems to be the best answer to the question of where on the ear the blood was sprinkled, for the following reason. As noted before, most animals don't have thumbs or big toes. Most also do not have lower ear lobes. One would thus find it hard to find any animal that has a big toe, and a thumb, and a lower ear lobe. Those are identifying characteristics of man. The Kohein, who represents the greatness of man, relating him to both Hashem and to other men, as well as to his spiritual essence, is thus sprinkled with both blood and oil on those uniquely human organs.